Claudio Trombini

The Ramsar site Pialassa Baiona is an intertidal brackish lagoon lying 5 km north of the city of Ravenna and covering a surface area of about 1,100 ha. From 1958 to 1976 Pialassa Baiona was heavily impacted by industrial pollution; mercury, polycyclic aromatic hydrocarbons, polymers were among the most important pollutants which nowadays contaminate the sedimentary compartment. Following earlier investigations on total mercury (THg) distribution and bioavailability, this study is focused on mercury speciation in sediments and clams. Methylmercury (MMHg) concentrations were determined in surface sediments (0-5 cm) in different seasons, and compared to THg. Selected sediments were subjected to a sequential extraction procedure to study solid state THg distribution. Operationally, three fractions of inorganic mercury were defined: mobile mercury (Hgm), humic acid complexed mercury (Hgha), and sulphide-bound mercury (Hgs). THg and MMHg concentrations in sediments ranged in the 0.2-250 mg g-1 and 0.13-45 ng g-1 d.w. intervals, respectively. MMHg / THg ratios were higher in summer as well as in sites where the THg burden was lower; the highest MMHg / THg values were observed in Chiaro del Pontazzo, an area subjected to a drastic reduction of salinity. THg and MMHg concentrations were also determined in tissues of clams (Tapes philippinarum) collected in the lagoon. MMHg in clams felt in the 180-470 ng g-1 interval and accounts for 72-95% of tissue THg.

106)

Role of volcanic dust in the atmospheric transport and deposition of polycyclic aromatic hydrocarbons and mercury.

Stracquadanio, Milena; Dinelli, Enrico; Trombini, Claudio.

Journal of Environmental Monitoring 2003, 5, 984-988.

Abstract

The role of volcanic ash as scavenger of atm. pollutants, in their transport and final deposition to the ground is examd.  Attention is focused on polycyclic arom. hydrocarbons (PAHs) and on particulate mercury (Hgp). The ash-fall deposits studied belong to the 2001 and 2002 eruptive activity of Mount Etna, Southern Italy, and were investigated at three (2001) and four (2002) sites downwind of the major tephra dispersal pattern.  The dry deposition of mercury and PAHs was detd., and, in particular, a downward flux to the ground of PAHs (apprx.7.29 mg m-2 per day) and mercury (750 ng m-2 per day) was estd. in Catania from Oct. 26 to Oct. 28, 2002.  Finally, evidence on the anthropogenic origin of PAHs scavenged from the troposphere by volcanic ash is supported by the anal. of PAH compns. in granulometrically homogeneous fractions.

105)

Indium-mediated coupling of 3-bromopropenyl acetate with (S)-Garner aldehyde: a route to 1,4-dideoxy-1,4-l-iminoribitol.

Lombardo, Marco; Licciulli, Sebastiano; Trombini, Claudio.

Tetrahedron Letters  2003, 44, 9147-9149.

Abstract

The indium organometallic complex generated by metallic indium and 3-bromopropenyl acetate in THF adds to the Garner aldehyde in excellent yield and with high diastereoselectivity; the usefulness of the corresponding anti-anti adduct was demonstrated by developing a short synthesis of the title compd., an azasugar known as a glycosidase inhibitor.

104)

3-Chloropropenyl pivalate in organic synthesis: the first asymmetric catalytic entry to syn-alk-1-ene-3,4-diols.

Lombardo, Marco; Licciulli, Sebastiano; Morganti, Stefano; Trombini, Claudio.

Chemical Communications  2003, 1762-1763.

Abstract

The first asym. catalytic synthesis of syn-alk-1-ene-3,4-diols was developed; the regio-, diastereo- and enantioselective addn. of 3-chloropropenyl pivalate to aldehydes was made possible by exploiting Salen-Cr(II) species, in a catalytic version of the Nozaki-Hiyama-Kishi reaction.

103)

Relationships between sediments and tissue contamination and allozymic patterns in Hediste diversicolor (Polychaeta Nereididae) in the Pialassa lagoons (north Adriatic Sea).

Virgilio, Massimiliano; Baroncini, Nicola; Trombini, Claudio; Abbiati, Marco.

Oceanologica Acta  2003, 26, 85-92.

Abstract

An increasing no. of studies showed that responses of populations to environmental stressors may be genetically dependent. Occurrence of genetic adaptation to high heavy metal concns. in Hediste diversicolor local ecotypes was also hypothesized. Analyses of allozymic patterns are a promising tool to genetically monitor environmental stressors. This study examd. whether the allozymic patterns of H. diversicolor could be affected by pollution levels. Five sites were investigated: 4 in a polluted brackish habitat, the Pialassa lagoons, and 1 ref. site in Lamone Estuary.  Total Hg was used as a tracer of the overall pollution level. Hg concns. were quantified in sediment and H. diversicolor tissue by cold vapor at. fluorescence spectroscopy.  A Hg concn. gradient in sediment and H. diversicolor tissue was obsd. Moreover, significant differences in Hg concns. were obsd. among and within sites.  Allozyme electrophoresis tested the occurrence of genetic differentiation among H. diversicolor samples.  A total of 19 putative gene loci were analyzed. For 6 gene loci, significant variability in genotypic and allelic frequencies was detected. Patterns of differentiation, which could be related to pollution levels, were obsd. at loci LDH, PGI, and SDH.  Other loci (ALD, FH, HBDH) showed a significant genetic structuring among samples not related to Hg concns.

102)

Migratory Aptitudes of Simple Alkyl Groups in the Anionotropic Rearrangement of Quaternary Chloromethyl Borate Species: A Combined Experimental and Theoretical Investigation.

Bottoni, Andrea; Lombardo, Marco; Neri, Andrea; Trombini, Claudio.

Journal of Organic Chemistry  2003, 68, 3397-3405.

Abstract

A combined exptl. and theor. study at the DFT and MP2 levels on the boron-to-carbon 1,2-shift in ate species, coming from the quaternization of boranes [RR1R2BCH2Cl]- (A) and boronate [cyclo-OQOB(CH2Cl)R]- (B), is reported. To discuss the different migratory aptitudes of various alkyl groups, the authors have examd. the migration of primary (R = Me, Et), secondary (R = iso-Pr), and tertiary (R = tert-Bu) alkyl groups. The effect of the counterion Li+ and of the solvent [polarized continuous model (PCM) method] was considered.  The following results are relevant: (a) in all cases, the reaction proceeds via a concerted-type mechanism which explains the retention of configuration at the migrating group and the inversion at the migration terminus exptl. obsd.  (b) The trend of the migration barriers along the direction primary ® secondary ® tertiary alkyl group obsd. in ate species A is reversed in boronate species B, in agreement with the exptl. evidences.  (c) A simple theor. model is proposed where the barrier trend is the result of a delicate interplay between two opposite factors: (1) a steric effect, which favors the most sterically demanding migrating groups, and (2) a charge effect assocd. with the partial carbanionic nature of the migrating carbon atom and which favors the less substituted migrating carbons.

101)

3-Bromopropenyl acetate in organic synthesis. The zinc-promoted a-hydroxyallylation of ketones.

Lombardo, Marco; Morganti, Stefano; d'Ambrosio, Francesca; Trombini, Claudio.

Tetrahedron Letters  2003, 44, 2823-2826.

Abstract

3-Bromo-propenyl acetate easily undergoes oxidative addn. by zinc, both under Barbier or Grignard conditions.  The resulting acetoxyallylzinc species are reported to react efficiently with ketones, thus widening the scope of the 3-bromo-propenyl acetate route to homoallylic alcs., e.g., I.  Barbier conditions in water or a Grignard two-step protocol in the THF/DMSO binary solvent system are used, depending on the ketone reactivity.

100)

3-Chloropropenyl esters in organic synthesis: a new chromium-catalyzed homoaldol reaction.

Lombardo, Marco; Morganti, Stefano; Licciulli, Sebastiano; Trombini, Claudio.

Synlett  2003, 43-46.

Abstract

Chromium(II) oxidatively adds to 3-halopropenyl esters affording heterosubstituted allylchromium(III) reagents exploitable in the Nozaki-Hiyama-Kishi reaction. A catalytic cycle based on the Cr(III)-Mn(0) redox couple was applied, affording protected homoaldols as the major products at 65° in acetonitrile.

99)

3-Bromopropenyl Esters in Organic Synthesis: Indium- and Zinc-Mediated Entries to Alk-1-ene-3,4-diols.

Lombardo, Marco; Morganti, Stefano; Trombini, Claudio.

Journal of Organic Chemistry 2003, 68, 997-1006.

Abstract

Metallic indium and zinc readily add to 3-bromopropenyl acetate and benzoate either in THF or in water, affording the corresponding 3-acyloxyallyl organometallic compds., which undergo further nucleophilic addn. to aldehydes RCHO (R = H2C=CMe, Me2CHCH2, cyclohexyl, 2-furyl, Ph, 4-MeOC6H4, etc.) to give alk-1-ene-3,4-diols H2C=CHCH(OH)CH(OH)R in good to excellent yields. Two synthetic protocols were developed, the former involving indium in THF under Grignard conditions and the latter involving zinc in aq. ammonium chloride under Barbier conditions.  The diastereoselectivity, under all the conditions examd., mainly depends on the nature of the carbonyl compd.; conjugated aldehydes afford syn adducts, while nonconjugated aldehydes display the anti stereopreference.

98)

The reaction of nitrones with organometallic compounds: scope, limitations and synthetic applications.

Lombardo, Marco; Trombini, Claudio.

Current Organic Chemistry, 2002, 6, 695-713.

A review.  In the last decade, the nucleophilic addn. of organometallic reagents to nitrones to give N,N-disubstituted hydroxylamines has been examd..  Grignard, lithium reagents and allylic zinc derivs. react very efficiently with nitrones in a wide temp. range; both the reaction rate and the stereochem. outcome of the process can be significantly modified by the addn. of nitrone-chelating Lewis acids.  The allylation of nitrones is also carried out under Sakurai conditions in the presence of trimethylsilyl triflate, and different results are obtained using allylic silanes or stannanes.  Homoallylic hydroxylamines, generated by the allylation of nitrones, are exploited in 5-exo-trig iodocyclizations to give 5-iodomethyl isoxazolidines, useful precursors of hydroxylated acyclic and cyclic amino compds. Enolates and silyl enol ethers under Mukayama conditions are also investigated. In particular, 2-trimethylsiloxyfuran reacts with nitrones, in the presence of nitrone activators, to give 3-substituted tetrahydrofuro[2,3-d]isoxazol-5(2H)-ones, easily transformed into a variety of polyhydroxylated piperidine and indolizidine azasugars. The most recent solns. to achieve control of stereochem. in nucleophilic addns. to nitrones will be examined.

97)

Regio- and stereoselective synthesis of homoallylic alcohols based on the use of (3-chloroprop-1-en-1-yl)boronates.

Lombardo, Marco; Morganti, Stefano; Tozzi, Massimo; Trombini, Claudio.

European Journal of Organic Chemistry, 2002, 2823-2830.

A set of (3-chloroprop-1-en-1-yl)boronates (CB) were synthesized, starting from (3-chloroprop-1-en-1-yl)bis(isopinocampheyl)borane. Quaternization of CB by Grignard methodol. afforded "ate" species, which underwent spontaneous anionotropic rearrangement to give the substituted allyl boronates.  By a suitable choice of the diol component in CB and of the reaction temp., a- or g-substituted allyl boronates could be selectively produced, offering routes to homoallylic alcs. or anti-alc., after treatment with an aldehyde.

96)

Mercury contamination of a coastal lagoon (Pialassa Baiona, Ravenna, Italy).

Fabbri, Daniele; Lombardo, Marco; Trombini, Claudio; Vassura, Ivano; Zavoli, Elisabetta; Horvat, Milena.

RMZ - Materials and Geoenvironment, 2001, 48, 186-192.

Abstract

Collection (in Dec., 1999, and July, 2000) and anal. of surface sediment samples from the Pialassa Baiona intertidal lagoon north of Ravenna, Italy, showed a south-north gradient of MeHg and showed that samples with a low Hg load had a higher percentage of MeHg relative to total Hg.  The amt. of mobile Hg, humic acid-complexed Hg , and sulfide-bound Hg were detd. in some samples. Differences in Hg speciation across the lagoon may reflect either different biogeochem. cycling or may be the result of a selective northward transport of the more mobile Hg species. The sediments of the Chiaro del Pontazzo, a freshwater pond that had been previously isolated at the south end of the lagoon contained high values of mobile Hg and the highest values of MeHg in the whole lagoon.

95)

The epicuticular wax of Laurus nobilis leaves as a passive sampler of polycyclic aromatic hydrocarbons in ambient air.

Marsili, Michelangelo; Stracquadanio, Milena; Trombini, Claudio; Vassura, Ivano.

Fresenius Environmental Bulletin  2001, 10, 26-30.

Abstract

Leaves of Laurus nobilis have been recently proposed as passive samplers of PAHs in ambient air. Since 4- and 5-ring polycyclic arom. hydrocarbons (PAHs) do accumulate in the epicuticular wax layer, an anal. protocol based on the extn. of intact leaves with dichloromethane is reported, followed by sepn. of PAHs from wax by partitioning them in the nitromethane-n-hexane biphasic system, and HPLC anal. Preliminary results of an air monitoring program of an industrial and an urban area in Ravenna are presented.

94)

The first zinc-promoted, environmentally friendly, and highly efficient acetoxyallylation of aldehydes in aqueous ammonium chloride.

Lombardo, Marco; Girotti, Rugiada; Morganti, Stefano; Trombini, Claudio.

Chemical Communications   2001, 2310-2311.

Abstract

An exceptionally mild acetoxyallylation of aldehydes in H2O promoted by Zn is reported, using 3-bromo-1-acetoxyprop-1-ene as starting material; simple diastereoselectivity mainly depends on the nature of the aldehyde.  Thus, reaction of PhCHO and BrCH2CH=CHOAc with 1.5 mmol Zn powder in satd. aq. NH4Cl for 30 min. afforded PhCH(OH)CH(OAc)CH=CH2 (90% yield, 65:35 syn:anti ratio). Similar reaction of c-C6H11CHO gave c-C6H11CH(OH)CH(OAc)CH=CH2 (83% yield, 10:90 syn:anti ratio).

93)

Anthropogenically derived mercury in sediments of Pialassa Baiona, Ravenna, Italy.

Fabbri, Daniele; Gemelli, Sabrina; Langone, Leonardo; Miserocchi, Stefano; Trombini, Claudio; Vassura, Ivano.

Annali di Chimica (Rome, Italy)  2001, 91, 563-575.

Abstract

Pialassa Baiona, a coastal wetland near the city of Ravenna, has been impacted for two decades (1958-1978) by industrial discharges contg. mercury and floating agglomerates of residues of polymn. processes.  Although the industrial use of mercury completely ceased in the early 90's, surface sediments are still highly contaminated, mercury concns. decreasing from the southern sub-basin, close to the discharge point, to the farthest northern border.  Concns. of total mercury, synthetic polymers (detd. by pyrolysis-GC/MS), total org. carbon, C/N ratio, total sulfur and 210Pb dating, were detd. in sediment cores collected in the southern and northern sub-basins.  Mercury and polymers exhibited parallel profiles with a peak corresponding to the historic emission record in the southern core, while in northern cores peaks of max. concn. display a delay reflecting the time required for the pollutants to migrate.  A recently developed mercury sequential extn. procedure was applied to the most polluted layers to study inorg. mercury speciation. Results indicate differences between the southern and northern areas, suggesting a more efficient binding of mercury to sediments in the southern sub-basin.

92)

A New Protocol for the Acetoxyallylation of Aldehydes Mediated by Indium in THF.

Lombardo, Marco; Girotti, Rugiada; Morganti, Stefano; Trombini, Claudio.

Organic Letters  2001, 3, 2981-2983.

A new precursor of a formal 1-hydroxy allyl anion is represented by 3-bromo-1-acetoxy-1-propene, which is synthesized by the ZnCl2-catalyzed addn. of acetyl bromide to propenal.

3-Bromo-1-acetoxy-1-propene reacts with indium powder in THF to give the corresponding 3-acetoxylated allyl indium complex, which regioselectively adds to aldehydes, affording monoprotected 1-en-3,4-diols. Diastereoselectivity mainly depends on the nature of the aldehyde; satd. aldehydes afford anti adducts, whereas the a,b-unsatd. aldehydes preferentially lead to the syn isomers.

91)

Distribution of mercury and other heavy metals in core sediments of the northern Adriatic Sea.

Fabbri, Daniele; Gabbianelli, Giovanni; Locatelli, Clinio; Lubrano, Debora; Trombini, Claudio; Vassura, Ivano.

Water, Air, and Soil Pollution  2001, 129, 143-153.

Abstract

Seven sediment cores were collected along a transect .apprx.20 Km off from the mouth of the Po River, in the northern Adriatic Sea (Italy).  Cores were characterized by different depositional sequences assocd. with late Pleistocene-Holocene lowstand (LST), transgressive (TST) and highstand (HST) system tracts.  Sediment samples were analyzed for Hg, Cu, Ni, Cr, Mn and Fe, as well as for total org. matter. Metal distribution generally showed vertical and spatial variability ascribed to grain size effects with no significant anthropogenic perturbation.  Conversely, Hg showed vertical profiles characterized by surface enrichment, with concns. in the upper layer (50-230 ng/g) exceeding 3-11 times the background value of 20 ng/g detd. in bottom cores.  Surface maxima were attributed to anthropogenic Hg delivered mainly by the Po River.

90)

Reading the chronicle of past industrial pollution in the sediments of a coastal lagoon. Pialassa Baiona, Ravenna.

Fabbri, Daniele; Trombini, Claudio; Vassura, Ivano.

Chimica e l'Industria (Milan, Italy)  2001, 83, e2/1-e2/4.

Abstract

North of Ravenna lies Pialassa Baiona, a brackish lagoon of both naturalistic (Ramsar Site) and economic value.  Past industrial effluents discharge left important traces in the sediments.  A map of surficial pollution by Hg is presented and preliminary results on the massive presence of polymeric materials (PVC and styrenics) and of polycyclic arom. hydrocarbons are reported.

89)

The hydroboration of propargyl chloride: a flexible one-pot three-component process easily directed towards the synthesis of (E)-homoallylic alcohols or anti-homoallylic alcohols.

Lombardo, Marco; Morganti, Stefano; Trombini, Claudio.

Synlett  (2001), 601-604.

Abstract

The hydroboration of propargyl chloride by a dialkylboranes affords 3-chloro-prop-1-en-1-yl boranes which, in the presence of a quaternary ammonium chloride, rearrange into allylic boranes, precursors of (E)-homoallylic alcs. (5) or anti-homoallylic alcs., (7) resp. Synthetic protocols for the selective generation of 5 and 7 were developed.

88)

Entropy-Controlled Selectivity in the Vinylation of a Cyclic Chiral Nitrone. An Efficient Route to Enantiopure Polyhydroxylated Pyrrolidines.

Lombardo, Marco; Fabbroni, Serena; Trombini, Claudio.

Journal of Organic Chemistry  2001, 66, 1264-1268.

Abstract

A short synthesis of 1,4-dideoxy-1,4-imino-L-arabinitol (LAB1) (I) and of 1,4-dideoxy-1,4-imino-D-galactitol (II), two aza sugars active as enzymic inhibitors, is reported.  The key reaction is the addn. of vinylmagnesium chloride to (3S,4S)-3,4-bis(benzyloxy)-3,4-dihydro-2H-pyrrole 1-oxide, a nitrone easily available from L-tartaric acid. Unexpectedly, the reaction affords the corresponding (2S,3S,4S)-1-hydroxy-2-ethenyl-3,4-bis(benzyloxy)pyrrolidine in very good yield and in 93/7 diastereomeric ratio (dr) independently of the reaction temp., thus representing a unique case of entropy-controlled reaction in a 100 K interval (from +20 °C to -80 °C). The trans intermediate 9 is converted in two steps (redn., N-protection) into the common intermediate (2S,3S,4S)-1-(benzyloxycarbonyl)-3,4-bis(benzyloxy)-2-ethenyl pyrrolidine. Double bond oxidn. followed by reductive debenzylation opens a route to the target pyrrolidine aza sugars I and II.

87)

The Hydroboration of Propargyl Bromide. Simple One-Pot Three-Component Routes to (Z)-1-Bromoalk-1-en-4-ols and to anti-Homoallylic Alcohols.

Lombardo, Marco; Morganti, Stefano; Trombini, Claudio.

Journal of Organic Chemistry  2000, 65, 8767-8773.

Abstract

The hydroboration of propargyl bromide with dialkylboranes takes place regioselectively to give 3-bromoprop-1-en-1-yl dialkylboranes which, upon quaternization with bromide ion, undergo a series of transformations into a no. of allylic boron species.  By a suitable choice of the exptl. conditions it is possible to trap the reaction intermediates with aldehydes and to steer the process toward either the synthesis of (Z)-1-bromoalk-1-en-4-ols or anti-homoallylic alcs.  Two one-pot three-component processes were developed based on a sequence of four reactions; prepn. of dialkylborane and hydroboration of propargyl bromide are the first steps.  Then, quaternization with TEBABr may be carried out either in the presence of the aldehyde when (Z)-1-bromoalk-1-en-4-ols are requested, or in the absence of the aldehyde in order to allow the formation of g-substituted allyl borane which, successively, adds to the aldehyde affording anti-homoallylic alcs.

86)

Use of Compound-Specific Stable Isotope Analysis to Source Anthropogenic Natural Gas-Derived Polycyclic Aromatic Hydrocarbons in a Lagoon Sediment.

McRae, Carole; Snape, Colin E.; Sun, Cheng-Gong; Fabbri, Daniele; Tartari, Daniele; Trombini, Claudio; Fallick, Anthony E.

Environmental Science and Technology  2000, 34, 4684-4686.

Abstract

This paper reports the 1st identification of polycyclic arom. hydrocarbons (PAHs) in the environment with extremely low C stable isotopic ratios.  For sediments from a coastal lagoon in northern Italy, these low 13C/12C isotopic ratios for many of the PAHs together with the presence of cylcopentafused PAHs (CP-PAH) indicate that the PAHs have predominantly been derived from a high-temp. industrial process utilizing the local biogenic natural gas.  The process used the biogenic gas as the feedstock for the prodn. of acetylene.  From the evidence available, the large variability in the PAH isotopic d13C values (from -31 to -62 ‰) is ascribed mainly to biodegrdn. rather than to major inputs from sources of isotopically heavy PAH, such as the neighboring modern-day carbon black plants.

85)

Nucleophilic additions to nitrones.

Lombardo, Marco; Trombini, Claudio.

Synthesis  2000, 759-774.

Abstract

A review with >87 refs. on reactions of nitrones with allylic organometallic compds., sulfur stabilized anions, acetylides, lithiated heteroarom. compds., etc. In addn., silylated nucleophiles are now routinely used under Mukaiyama conditions to give useful mild approaches to functionalized isoxazolidines. Attention has been also paid to the development of stereocontrolled processes; nitrones derived from glyceraldehyde and congeners have been carefully studied and interesting reversions of facial selectivity have been reported by complexing them with Lewis acids. N-Glycosyl nitrones are used to synthesize enantiomerically enriched amines after cleavage of the auxiliary group and redn. of the N-O bond.  Very few attempts at reactions based on chiral catalysts have been reported. So far, asym. catalysis has not found proper applications, and the opportunities offered by nitrones will represent a major challenge in this field.

84)

Analysis of poly(vinyl chloride) and other polymers in sediments and suspended matter of a coastal lagoon by pyrolysis-gas chromatography-mass spectrometry.

Fabbri, D.; Tartari, D.; Trombini, C.

Analytica Chimica Acta  2000, 413, 3-11.

Abstract

Pyrolysis-gas chromatog.-mass spectrometry (Py-GC-MS) was used for the anal. of synthetic polymers in core sediments and suspended particulate matter (SPM) of the coastal lagoon Pialassa Baiona (Adriatic Sea). Pyrograms exhibited a multitude of peaks deriving from the thermal degrdn. of natural org. matter (humic substances, planktonic material), artificial resins and synthetic rubbers.  Upon pyrolysis, sediments generated high levels of styrene and benzene and a series of arom. hydrocarbons (a-methylstyrene, indene, naphthalenes, biphenyl, diphenylpropane) indicative of the presence of vinyl polymers (e.g. poly(vinyl chloride), polystyrene), whereas markers for rubbers (butadiene dimer, styrene-butadiene) were identified in pyrograms of SPM. Concns. of styrene polymers (expressed as polystyrene, PS) and poly(vinyl chloride) (PVC) were estd. in sediment cores by Py-GC-MS using the evolved benzene and styrene for quantitation, and values greater than 1 mg/g were obsd. in the most polluted layers.  Plastic materials were isolated from sediments by Soxhlet-extn. with dichloromethane followed by pptn. in n-hexane and analyzed by Py-GC-MS and spectroscopic techniques (1H- and 13C-NMR spectroscopy, FTIR). PVC made up the bulk of the isolated polymers which were found at concns. up to 55 mg/g. PVC concns. detd. by both methods (direct pyrolysis and polymer extn.), showed maxima in subsurface strata and were strongly correlated with Hg concns.  This finding suggests that the presence of resins is due to past industrial activity, even though the identification of styrene-plastic rubbers in SPM indicates that polymers are still redistributed and/or discharged into the lagoon.

83)

Trimethylsilyl triflate-promoted addition of 2-trimethylsilyloxyfuran to a chiral cyclic nitrone; a short synthesis of [1S(1a,2b,7b,8a ,8aa)]-1,2-di(t-butyldiphenylsilyloxy) indolizidine-7,8-diol.

Lombardo, Marco; Trombini, Claudio.

Tetrahedron  2000, 56, 323-326.

Abstract

The trimethylsilyl triflate promoted addn. of 2-trimethylsilyloxyfuran to (3S,4S)-3,4-dihydro-3,4-di(t-butyldiphenylsilyloxy)-2H-pyrrole 1-oxide, derived from (R,R)-tartaric acid, displays complete facial selectivity, affording two diastereomeric butenolides in excellent overall yield.  The major adduct undergoes silica-gel induced ring-closure to give in almost quant. yield [4S(4a,5b,5ab,5-ba,8aa)]-hexahydro-4,5-di(t-butyldiphenylsilyloxy)-pyrrolo[1,2b]furo[2,3d]isoxazol-7(3H)one; redn. with DIBAH followed by hydrogenolysis on Pd(OH)2/C affords the partially protected 1,2,7,8-indolizidinetetrol I.

1999-1995

Keywords:

organic synthesis (nitrone chemistry, Lewis acid promoted condensations, azasugars, regioselective anionic polymerization);

environmental chemistry (mercury polluted wetlands, mercury speciation, methylmercury analysis, pyrolytic determination of polymers).

82)

Biomonitoring of mercury pollution in a wetland near Ravenna, Italy, by translocated bivalves (Mytilus galloprovincialis).

Cattani, Otello; Fabbri, Daniele; Salvati, Marco; Trombini, Claudio; Vassura, Ivano.

Environmental Toxicology and Chemistry  1999, 18, 1801-1805.

Abstract

An active biomonitoring expt. using mussels (Mytilus galloprovincialis) was performed in Pialassa Baiona, a mercury-polluted coastal wetland near Ravenna, Italy.  Three stations (A, B, and C) were selected along the south to north axis.  Following a 52-d field exposure, organisms transplanted in the southernmost polluted area (station A) showed mean mercury concn. values of 660 ng/g (dry wt.), 4.4 times the initial background level, and were still accumulating mercury.  Mussels in both the central area (station B) and the northern area (station C) seemed to reach a steady state with mean mercury concn. values of 323 and 412 ng/g, resp.  This field expt. is the first study carried out in the Ravenna wetlands to evaluate mercury bioavailability in this environment.  Finally, the efficiency of the population of Mytilus galloprovincialis selected for the field expt. as mercury bioaccumulators was tested in a lab. expt. that revealed that up to 135 mg/g (dry wt.) could be reached after 77 d of exposure to mercury-polluted water.

81)

One-pot multicomponent reactions.

Lombardo, Marco; Trombini, Claudio.

Seminars in Organic Synthesis, Summer School "A. Corbella", 1998, 7-32.

23rd, Gargnano, Italy, June 15-19, 1998. Publisher: Societa Chimica Italiana, Rome, Italy.

Abstract

Review with 85 refs.

80)

Analysis of polystyrene in polluted sediments by pyrolysis-gas chromatography-mass spectrometry.

Fabbri, Daniele; Trombini, Claudio; Vassura, Ivano.

Journal of Chromatographic Science  1998, 36, 600-604.

Abstract

The use of pyrolysis combined with gas chromatog. and mass spectrometry for the anal. of polystyrene in sediments is described.  The method is applied to a sediment core of the Lagoon of Ravenna (Pialassa Baiona); in these sediments, polystyrene is detected at mg/g levels in surface layers.  Dried sediment samples are directly pyrolyzed in a quartz tube holder, the peak area of the evolved styrene is detd. in the single ion monitoring mode, and polystyrene concn. is calcd. from the appropriate calibration curve.  Linear plots of styrene peak area vs. polystyrene content are obtained by pyrolyzing the polymer in the presence of various matrixes: calcite, quartz, kaolinite, montmorillonite, and whole sediment.  The pyrolytic behavior of polystyrene is strongly affected by the presence of clay minerals, whereas calcite and quartz exhibit a lower influence.  The effect of other org. constituents, such as humic substances and styrenebutadiene rubbers, is discussed.

79)

A route to (2a,3b,4a)-( ±)-2-(hydroxymethyl)-3,4-pyrrolidine-diol based on the a-silyloxyallylation of a glycolaldehyde-derived nitrone.

Lombardo, Marco; Spada, Simone; Trombini, Claudio.

European Journal of Organic Chemistry  1998, 2361-2364.

A protected form I of the title compd., whose two enantiomers are known to be potent a-glycosidase inhibitors, was obtained through a 5-step synthesis based on 2 thoroughly diastereo-controlled steps. An anti-selective a-silyloxyallylation of nitrone Me3CMe2SiOCH2CH:N+(CH 2Ph)O- afforded hydroxylamine II which, after O-silylation, was subjected to iodocyclization to give 5-iodomethylisoxazolidine III as a single diastereomer.  Displacement of iodide by mesylate and subsequent hydrogenolysis of the mesylate furnished I in 20% overall yield starting from Me3CMe2SiOCH2CHO.

78)

A one-pot three-component route to anti-homoallylic alcohols based on the hydroboration of propargyl bromide.

Gaddoni, Lorenzo; Lombardo, Marco; Trombini, Claudio.

Tetrahedron Letters  1998, 39, 7571-7574.

Abstract

(3-Bromoalken-1-yl)dialkylboranes, generated by hydroboration of propargyl bromide with dialkylboranes, smoothly rearrange to (E)-allylic boranes, which can be trapped with aldehydes. The resulting one-pot three-component sequence represents a route to anti-homoallylic alcs. in fairly good yields.

77)

The Lagoon of Ravenna(Italy): characterization of mercury-contaminated sediments.

Fabbri, D.; Felisatti, O.; Lombardo, M.; Trombini, C.; Vassura, I.

Science of the Total Environment  1998, 213, 121-128.

From 1958 to 1973, the wetland called Pialassa Baiona near Ravenna, Italy, was heavily polluted by industrial effluents, among which Hg was the most hazardous contaminant.  Three sediment cores representative of a channel and a pond in the southern area, close to the discharge point, were analyzed.  Up to 244 mg/g dry wt. Hg was obsd. in the top 0-20 cm layer.  Among various parameters under study, good correlation was found among Hg and redox properties of the sediment, S, and org. matter.  Styrene/butadiene-based polymers, produced in the same industrial area since 1958, were an important component of org. matter.  Despite the analogy with the Minamata case, Hg appears to be efficiently trapped by the sediment, probably in the form of sulfide and/or bound to org. matter; so far, it has not represented a public health hazard as confirmed by lack of epidemiol. effects in the Ravenna area due to Hg exposure.

76)

Trimethylsilyl triflate promoted addition of allyltributylstannane to aldonitrones. One-pot synthesis of 5-(iodomethyl)isoxazolidines.

Gianotti, Massimo; Lombardo, Marco; Trombini, Claudio.

Tetrahedron Letters  1998, 39, 1643-1646.

Abstract

The trimethylsilyl triflate promoted allylation of nitrones with allyltributylstannane affords O-silylated hydroxylamines in high yield. When the crude reaction mixt. is quenched with N-iodosuccinimide, 5-(iodomethyl)isoxazolidines are formed in excellent yields. The overall one-pot, two-step process represents a valuable improvement in terms of time, cost and overall yield with respect to the previously reported three-stage procedure involving nitrone allylation, hydroxylamine O-silylation, and iodocyclization.

75)

Anionic copolymerization of conjugated dienes and vinyl arenes in the presence of alkyl ethers of tetrahydropyranyl methanol.

Viola, Gian Tommaso; Trombini, Claudio; Musiani, Lorenzo.

Eur. Pat. Appl. (1998), 10 pp. - (Enichem S.p.A., Italy).

CODEN: EPXXDW  EP  856532  A1  19980805  Designated States R: BE, DE, ES, FR, GB, RO.  Patent  written in English.    Application: EP  97-107420  19970506.  Priority: IT  97-171  19970130.  CAN 129:162673    AN 1998:527115    CAPLUS   (Copyright 2003 ACS on SciFinder (R)) 

Patent Family Information

Patent No.                   Kind                Date                Application No.                        Date 

EP  856532                 A1                  19980805       EP  1997-107420           19970506

EP  856532                 B1                   20010926                                             

R:  BE, DE, ES, FR, GB, RO

ES  2160867               T3                   20011116       ES  1997-107420           19970506

US  5914378               A                    19990622       US1997-852688           19970507

CA 2206263               AA                  19980730       CA 1997-2206263         19970513

TW 474951                 B                     20020201       TW                                 1997-86107207       19970524

JP   10218908             A2                  19980818       JP   1997-135504           19970526

CN 1189508               A                    19980805       CN 1997-113179           19970530

BR  9703333               A                    19980915       BR 1997-3333               19970530 

Priority Application

IT   1997-MI171         A                    19970130

74)

A nitrone-based route to polyhydroxylated lactams and piperidines. An expeditious synthesis of rac-fagomine.

Degiorgis, Fabio; Lombardo, Marco; Trombini, Claudio.

Synthesis  1997, 1243-1245.

Abstract

The synthetic versatility of tetrahydrofuro[2,3-d]isoxazol-5(2H)-ones, obtained from Me3SiO3SCF3-promoted addn. of 2-(trimethylsilyloxy)furan to nitrones, is demonstrated in a 2-step reductive sequence to give the title compds.  The cycloadducts obtained from a glycolaldehyde-derived nitrone are first reduced with DIBAH and then hydrogenolyzed in the presence of Pd(OH)2 to give polyhydroxylated piperidines, including rac-fagomine.  Direct hydrogenolysis of the same cycloadducts gives an easy entry to polyhydroxylated lactams.

73)

Synthesis of four stereoisomers of 5-amino-2,5-dideoxy-heptono-1,5-lactams.

Degiorgis, Fabio; Lombardo, Marco; Trombini, Claudio.

Tetrahedron  1997, 53, 11721-11730.

Abstract

The reaction of 2-(trimethylsiloxy)furan with a glyceraldehyde nitrone was examd. under different conditions. The four intermediates, stereoisomers of tetrahydrofuro[2,3-d]isoxazol-5(2H)-one I, were sepd. by combined chromatog.-crystn. techniques. The synthetic versatility of I was demonstrated by a direct high-yield conversion to 5-amino-2,5-dideoxy-heptono-1,5-lactam (II) stereoisomers upon simple hydrogenolysis in the presence of Pearlman catalyst.

72)

Synthesis and Iodocyclization of Homoallylic Hydroxylamines.

Fiumana, Andrea; Lombardo, Marco; Trombini, Claudio.

Journal of Organic Chemistry  1997, 62, 5623-5626.

Abstract

Allylic zinc bromides prepd. from allylic bromides and zinc powder in THF regioselectively react with nitrones to give homoallylic hydroxylamines in very good yields. The stereochem. outcome using crotyl zinc bromide and prochiral nitrones or allyl zinc bromide and the N-benzyl nitrone of (R)-glyceraldehyde can be reversed by the addn. of diethylaluminum chloride. The iodocyclization reactions of the resulting homoallylic hydroxylamines are explored.

71)

Synthesis of 3-O-benzyl-3,7-imino-1,3,6,7-tetradeoxy-L-manno-heptitol and of 3-O-benzyl-3,7-imino-1,3,6,7-tetradeoxy-D-gluco-heptitol.

Degiorgis, Fabio; Lombardo, Marco; Trombini, Claudio.

Organic Preparations and Procedures International  1997, 29, 485-488.

Abstract

We report a short synthesis of enantiomerically pure piperidines via a simple manipulation of tetrahydrofuro[2,3-d]isoxazol-5(2H)ones.  The present synthetic sequence can be applied to a variety of starting nitrones thus affording an easy entry to 2-substituted 3,4-dihydroxypiperidines.

70)

A new route to amino sugars from sugar nitrones: preparation of 6-deoxynojirimycin.

Dhavale, Dilip D.; Desai, Vijaya N.; Sindkhedkar, Milind D.; Mali, Raghao S.; Castellari, Carlo; Trombini, Claudio.

Tetrahedron: Asymmetry  1997, 8, 1475-1486.

Abstract

The 1,3-addn. of methylmagnesium chloride to dialdose derived nitrones afforded N-benzylhydroxylamines in high yields.  The stereoselectivity of the addn. reaction was improved by the use of trimethylsilyl triflate. The N-O bond reductive cleavages of N-benzylhydroxylamines took place in good yields and offered an easy access to N-benzylamino sugars. The potential of these amino sugars is demonstrated by the prepn. of glycosidase inhibitor 6-deoxynojirimycin.

69)

Copolimerizzazione anionica di dieni coniugati e vinilareni in presenza di dialchileteri del tetraidropiranilmetanolo.

Bortolotti, Michele; Viola, Gian Tommaso; Musiani, Lorenzo; Trombini, Claudio.

Brevetto Italiano IT-A-MI 1996 1132 - (Enichem S.p.A., Italy).

68)

Stereoselective synthesis based on zinc and boron enolates.

Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Advances in Carbanion Chemistry  1996, 2, 111-146.

Abstract

Recent achievements in stereocontrolled org. transformations exploiting Zn and B enolates, mainly in reactions with carbonyl compds., are reviewed with over 122 refs.  Although the aldol condensation of these enolates involves a common mechanistic picture, different behavior is obsd.  Thus, while Zn enolates are generally considered to offer poor stereocontrol, aldol condensations promoted by B enolates are highly diastereoselective.  Particularly good results were recorded in the field of b-lactam syntheses, where Zn enolates afford a fruitful reverse stereochem. trend with respect to Li enolates.  Also, the control of the abs. stereochem. in the reactions of using chiral ligands is presented.  The chem. of B enolates has reached a high level of sophistication.  The direct borylation-enolization route to B enolates allows one to obtain syn or anti, Cram or anti-Cram aldols of the desired abs. configuration by an appropriate choice of the B ligands and other exptl. conditions. The less accessible thermodn. B enolates can be regio- and stereoselectively prepd. by indirect routes such as the conjugate addn. of dialkylboranes to a,b-enones.  Stress is placed on total syntheses of complex mols. in which B and Zn enolates play the role of key reagents in a crit. asym. step.

67)

Lewis-acid promoted addition of 2-trimethylsilyloxyfuran to nitrones: synthesis and absolute configuration of tetrahydro-2-benzyl-3-(1-benzyloxyethyl)-furo[2,3-d]isoxazol-5(2H)ones.

Castellari, Carlo; Lombardo, Marco; Pietropaolo, Graziano; Trombini, Claudio.

Tetrahedron: Asymmetry  1996,  7,  1059-1068.

A straightforward synthesis of tetrahydro-2-benzyl-3-(1-benzyloxyethyl)-furo[2,3-d]isoxazol-5(2H)ones is reported, based on the Lewis acid-catalyzed addn. of 2-trimethylsilyloxyfuran to the N-benzyl nitrone of (S)-lactaldehyde.

66)

Synthesis and Photophysical Properties of Fluorescent Derivatives of Methylmercury.

Bolletta, Fabrizio; Fabbri, Daniele; Lombardo, Marco; Prodi, Luca; Trombini, Claudio; Zaccheroni, Nelsi.

Organometallics  1996, 15, 2415-17.

Abstract

New fluorescent methylmercury acetylides carrying the anthracene, acridinone, and dansyl frameworks have been prepd. and photophys. characterized.  These compds., which partially retain the fluorescence properties of the parent alkynes, suggest a promising use as luminescent labels for the anal. of methylmercury.

65)

A new procedure for the speciation of mercury in water based on the transformation of mercury(II) and methylmercury(II) into stable acetylides followed by HPLC analysis.

Fabbri, Daniele; Lombardo, Marco; Trombini, Claudio; Vassura, Ivano.

Applied Organometallic Chemistry  1995, 9, 713-18.

Abstract

Conversion of mercury(II) and methylmercury(II) species dissolved in water into di(phenylethynyl)mercury and methyl(phenylethynyl) mercury takes place in satisfactory yield under alk. conditions by stirring the aq. soln. with phenylacetylene at room temp.  Mercury speciation is simply obtained by HPLC anal. of the two organometallic species.  The presence of heavy metals such as copper(II), zinc(II), cadmium(II) and lead(II) in concns. 10,000 times higher than mercury is tolerated, while little interference is displayed by humic acids and cysteine.  Seawater samples can also be analyzed following a property adapted procedure.

64)

Regioselective addition of 1-trimethylsilyloxy-1-methoxy-1,3-dienes to aldonitrones catalyzed by trimethylsilyl triflate.

Camiletti, Chiara; Dhavale, Dilip D.; Donati, Franco; Trombini, Claudio.

Tetrahedron Letters  1995, 36, 7293-6.

Abstract

1-Trimethylsilyloxy-1-methoxy-1,3-dienes (3a-d) regioselectively add to aldonitrones at -20° in dichloromethane in the presence of 10-20% of trimethylsilyl triflate to give g-adducts in high yields; on the other hand, 1-trimethylsilyloxy-1-methoxy-1,3-hexadiene (3e) displays a reversed regiochem. preference affording the a-adduct as the major product.

1994-1990

Keywords:

nitrone chemistry (nucleophilic additions to nitrones, iodocyclization of homoallylic hydroxylamines);

boron chemistry (1,4-addition of secondary boranes to a,b -enones, boron enolates);

asymmetric synthesis (chiral auxiliaries for the enantioselective acylation of enolates, catalytic asymmetric allylation of aldehydes).

63)

Trimethylsilyl Trifluoromethanesulfonate-Catalyzed Reaction of 2-[(Trimethylsilyl)oxy] furan with Nitrones.

Camiletti, Chiara; Poletti, Laura; Trombini, Claudio.

Journal of Organic Chemistry  1994, 59, 6843-6.

Abstract

The reaction of 2-trimethylsilyloxyfuran (5) with nitrones 1a-j R1C=N+(O-)R2 (R1 = Ph, 2-thienyl, 1-naphthyl, Me2CH, Me3C, R2 = Me; R1 = Et, Me2CH, Me3C, Ph, 2-thienyl, R2 = CH2Ph) is catalyzed by trimethylsilyl trifluoromethanesulfonate and gives rise to 2(5H)-furanone 5-N-hydroxymethanamines 8 which are quant. converted by silica gel into bicyclic isoxazolidines 6 (shown as I; same R1, R2).  Reactions take place in good to excellent yields and the stereochem. outcome of the cycloaddn. process can be anticipated on the basis of the nature of the nitrone substituents R1 and R2. 

62)

A novel derivatization procedure for inorganic mercury(II) for HPLC analysis.

Fabbri, D.; Trombini, C.

Chromatographia  1994, 39, 246-8.

Abstract

A new procedure for derivatization of inorg. mercury(II) to diphenylethynylmercury with simultaneous extn. into dichloromethane is proposed. The organomercury deriv. is effectively analyzed by HPLC using UV detection. The calibration curve is linear over three orders of magnitude (0.02-50 mg L-1 Hg); the detection limit is 0.1 ng Hg. A preliminary study of the effect of potential interfering agents, in particular Cu(II), Zn(II), Cd(II), Pb(II), and cysteine, and applications of the present methodol. to real environmental samples are presented.

61)

Trimethylsilyl trifluoromethanesulfonate-promoted cycloaddition of nitrone with silyl enol ethers: synthesis and reactivity of 5-siloxyisoxazolidines.

Camiletti, Chiara; Dhavale, Dilip D.; Gentilucci, Luca; Trombini, Claudio.

Journal of the Chemical Society, Perkin Transactions 1  1993, 3157-65.

In the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf), the reaction of nitrones, R2N(O)=CR1 (e.g., R1 = Et, R2 = CH2Ph), with sily enol ethers, CH2=CR3OR4 (e.g., R3 = H, R4 = SiMe2CMe3), affords 5-siloxyisoxazolidines I under mild conditions, in good to excellent yields. 5-Siloxyisoxazolidines, e.g., I, can undergo chemoselective redns. to Mannich bases or N-hydroxy-1,3-amino alcs., and, in the presence of TMSOTf, react with silylated carbon nucleophiles at the acetalic C-5 carbon to give, for example, 5-allyl- and 5-cyano-isoxazolidines. 

60)

Catalytic asymmetric synthesis of homoallylic alcohols.

Costa, Anna Luisa; Piazza, Maria Giulia; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the American Chemical Society  1993, 115, 7001-2.

Abstract

Catalytic asym. allylation of aldehydes was realized by using allyltributyltin as allylating agent and a TiCl2-binaphthol complex as chiral catalyst.  This procedure seems to be applicable to any type of aldehyde, affording homoallylic alcs. in good yields; enantioselectivity is very good and exceptionally high in the case of straight chain aliph. substrates (>97% e.e.).

59)

Trimethylsilyl triflate-promoted [2+3] dipolar cycloaddition of nitrones with allyltrimethylsilane.

Dhavale, Dilip D.; Trombini, Claudio.

Heterocycles  1992, 34, 2253-8.

Abstract

3-Alkyl-5-trimethylsilylmethylisoxazolidines, e.g. I (R = Me, Et, Me2CH, Me3C; R1 = CH2Ph, Me) are accessible in good yields and at temps. £ 20°, by the trimethylsilyl triflate-promoted cycloaddn. reaction of allyltrimethylsilane with aliph. nitrones. 

58)

Iodocyclization of homoallylic hydroxylamines derived from D-glyceraldehyde.

Dhavale, Dilip D.; Gentilucci, Luca; Piazza, Maria Giulia; Trombini, Claudio.

Liebigs Annalen der Chemie  1992, 1289-95.

Abstract

The reaction of allylmagnesium chloride with nitrone I derived from D-glyceraldehyde affords two diastereoisomeric homoallylic hydroxylamines II (R = H) which, after sepn. and O-silylation, are subjected to iodocyclization using N-iodosuccinimide.  The stereochem. outcome of the cyclization reaction was found to be different; thus, S-(R*,R*)-II (R = SiMe2CMe3) is converted into a mixt. of cis- and trans-isoxazolidines III in which the trans product prevails, whereas S-(R*,S*)-II (R = SiMe2CMe3) is stereoselectively converted into the cis-isoxazolidine IV.  The final 5-(iodomethyl)isoxazolidines III and IV may be easily subjected to further studies; for example, they undergo iodine displacement by treatment with azide, phthalimide, and acetate ions to give formal precursors of deoxy-amino-hexitols.

57)

Trimethylsilyl trifluoromethanesulfonate promoted [3 + 2] dipolar cycloaddition of nitrones and silyl enol ethers: an efficient route to 5-siloxyisoxazolidines.

Dhavale, Dilip D.; Trombini, Claudio.

Journal of the Chemical Society, Chemical Communications  1992 1268-70.

Abstract

The reaction of silyl enol ethers, CH2=CR3OSiMe2R4 (R3 = H, Me, Ph, R4 = Me, Me3C), and nitrones, R1CH=N+R2O- (R1 = Et, CHMe2, CMe3, Ph, R2 = Bn, Me), in the presence of trimethylsilyl trifluoromethanesulfonate, gives 5-siloxyisoxazolidines I in excellent yield under fairly mild conditions.  Isoxazolidines II, a presumed decompn. product of I, were also isolated.

56)

Chiral orthoesters in organic synthesis: novel reagents for the enantioselective acylation of silyl enol ethers.

Longobardo, Luigi; Mobbili, Giovanna; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Tetrahedron  1992, 48, 1299-316.

Abstract

Dialkyl trans-2-alkoxy-2-alkyl-1,3-dioxolan-4,5-dicarboxylates and the corresponding N,N,N,N-tetramethyl-4,5-diamides were prepd. from dialkyl tartrates or tartaric acid diamides, resp.  They smoothly reacted with silyl enol ethers in the presence of Lewis acids to give enantiomerically enriched (up to 90% d.e.) monoprotected 1,3-diketones.  A dramatic dependence of the stereochem. outcome from the configuration of the enolic double bond of 1-(trimethylsiloxy)cyclohex-1-ene was obsd.  The products can be stereoselectively reduced to give configurationally defined monoprotected 3-ketols.

55)

An MC-SCF study of the transition structures for the aldol reaction of formaldehyde with acetaldehyde boron enolate.

Bernardi, Fernando; Robb, Michael A.; Suzzi-Valli, Giorgio; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  (1991), 56(22), 6472-5.

Abstract

The transition state region of the aldol reaction of ethenyloxyborane, the simplest acetaldehyde boron enolate, with formaldehyde has been investigated at the 3-21G MC-SCF level. Three six-member cyclic transition structures have been identified as twist-boat, chair and half-chain structures. The twist-boat structure is found to be more stable than the chair structure by 1.7 Kcal/mol and more stable than the half-chain structure by 2.45 Kcal/mol.

54)

A new protocol for regio- and stereocontrolled aldol reactions through the conjugate addition of dialkylboranes to a,b-unsaturated ketones.

Boldrini, Gian Paolo; Bortolotti, Michele; Mancini, Fabrizio; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1991, 56, 5820-6.

Abstract

A one-pot, two-step procedure, consisting of the 1,4-addn. of dialkylboranes to b-substituted (E)-a,b-unsatd. ketones followed by the reaction of the resulting configurationally pure (Z)-(vinyloxy)boranes with aldehydes, is reported.  The overall process corresponds to a regio- and stereocontrolled aldol addn. of an unsym. ketone to an aldehyde. A concerted 1,4-addn. mechanism accounts for the stereochem. outcome of the hydroboration reaction; cyclic enones do not undergo conjugate addn., while (Z)-b-substituted or b,b-disubstituted a,b-unsatd. ketones still react in a 1,4-fashion, but with a slower rate and a lower degree of chemoselectivity with respect to b-substituted (E)-a,b-unsatd. ketones.  In the cases of a,b-disubstituted a,b-unsatd. ketones and (E)-(S-phenylthio)cinnammate, which react with dicyclohexylborane to give a mixt. of E and Z enolates, an alternative mechanism is proposed.

53)

Stereoselective 1,4-hydroboration of acyclic (E)-a,b-unsaturated ketones with dialkylboranes.  Synthesis of (Z)-vinyloxyboranes.

Boldrini, Gian Paolo; Bortolotti, Michele; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Tetrahedron Letters  (1991), 32(9), 1229-32.

Abstract

Dialkylboranes add to acyclic disubstituted (E)-a,b-unsatd. ketones in a 1,4-fashion affording (Z)-vinyloxyboranes as major or sole products. The stereochem. outcome of the hydroboration reaction is consistent with a concerted pericyclic mechanism. The intermediate vinyloxyboranes can be trapped with aldehydes to give virtually pure syn b-hydroxyketones.  Thus, hydroboration of CH3CH=CHCOCH2CH3 with di-2-isocaranylborane in CHCl3 gave vinyloxyborane intermediate, identified by NMR, which on condensation with PhCHO gave 83% syn-PhCH(OH)CHEtCOCH2CH3 in 31% enantiomeric excess.

52)

Enantioselective acylation of enolates: the reaction of (4R)-trans-diethyl-2-alkyl-2-methoxy-1,3-dioxolane-4,5-dicarboxylates with (E)- and (Z)-silyl enol ethers.

Basile, Tiziana; Longobardo, Luigi; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Chemical Communications  1991, 391-2.

Abstract

Dioxolanedicarboxylates I (R = Me, Et, Pr) enantioselectively acylated R1CH=CR2(OSiMe3) (II, R1 = Me, Et, Pr; R2 = Et, Pr) to give mono-protected 1,3-diketones III.  The stereoselectivity is strongly affected by the double bond configuration.  Both (Z)- and (E)-II were acylated in good yields, but the Z-isomers give a 1:1 ratio of diastereomeric diketones, while excellent stereoselectivities were obtained with E-enols. 

51)

A new route to 3,5-disubstituted isoxazolidines via the iodocyclization of homoallylic hydroxylamines.

Mancini, Fabrizio; Piazza, Maria Giulia; Trombini, Claudio.

Journal of Organic Chemistry  1991, 56, 4246-52.

Abstract

N,N-Dialkyl-O-trialkylsilyl homoallylic hydroxylamines reacted with iodine, N-iodosuccinimide, or iodine chloride to give 3,5-disubstituted isoxazolidines, e.g. I (R = Ph, R1 = Me, CH2Ph, CMe3), in good yield.  The relative configuration that was generated at C3 and C5 was controlled by the nature of the nitrogen substituent of the parent hydroxylamine: the presence of a primary alkyl group favored the formation of a cis-isoxazolidine, whereas the presence of a tert-Bu group favored the formation of a trans-isoxazolidine. The effects that the N- and O-substituents and the nature of the iodinating agent exerted on the stereoselectivity of the cyclization were examd. The synthesis of enantiomerically pure isoxazolidines from hydroxylamines carrying a chiral N-mannofuranosyl group, is described.

50)

A new approach to (Z)-vinyloxyboranes via 1,4-hydroboration of (E)-a,b-unsaturated ketones. Synthesis of syn aldols.

Boldrini, Gian Paolo; Mancini, Fabrizio; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Chemical Communications  1990, 1680-1.

(Z)-Vinyloxyboranes are obtained via 1,4-hydroboration of acyclic disubstituted (E)-a,b-unsatd. ketones, e.g., PhCH=CHCOMe, with dicyclohexylborane or diisopinocampheylborane in THF, CH2Cl2 or CHCl3 at 20°; treatment of the hydroboration mixt. with an aldehyde, e.g., BzH, allows pure syn aldols, e.g., I, to be synthesized in 54-91% yields, and in excellent enantiomeric excesses, by using the latter borane.

49)

Novel enantioselective acylating agents.  The reactions of chiral ortho esters and silylenol ethers as a route to optically active monoprotected 1,3-dicarbonyl compounds.

Basile, Tiziana; Longobardo, Luigi; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Chemical Communications  1990, 759-60.

Abstract

A novel enantioselective route to monoprotected 2-substituted-1,3-dicarbonyl compds. I (R = Me, Et, Ph, R1 = Et, n = 1; R = Me, R1 = CHMe2, n = 1; R = Me, R1 = Et, n = 0, 2) has been developed via acylation of silyl enol ethers II with chiral orthoesters III. Good yields and stereoselectivity can be achieved starting from cyclic enol silanes.

48)

Synthesis of 3-alkoxyalkanoic esters from acetals. A novel application of Reformatsky reagents in asymmetric synthesis.

Basile, Tiziana; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Synthesis  (1990), (4), 305-11.

Abstract

Reformatskii reagents react with acetals in the presence of TiCl4 or BF3×Et2O to give alkoxyalkanoic esters.  Thus, PhCH(OMe)2 reacted with BrZnCHMeCO2Et in the presence of TiCl4 in CH2Cl2 to give 54 and 26% erythro- and threo-MeOCHPhCHMeCO2Et resp. When chiral acetals were used as substrates up to 84% enantiomerically enriched 3-hydroxyalkanoic esters could be prepd.

1989-1985

Keywords:

asymmetric synthesis (enantiopure boron enolates, enantiopure hypervalent allylic and propargylic stannanes, chiral pool strategy, prostanoids from D-glucose).

heterogeneous reagents and catalysts (zinc, tin and titanium on graphite; nickel-catalyzed transfer hydrogenation).

47)

Negative ion mass spectra of b-nitro alcohols.

Romano, Anna Maria; Trombini, Claudio; Zuppiroli, Luca.

Organic Mass Spectrometry  1989, 24, 1025-7.

The negative-ion mass spectra of 11 title compds. were recorded, and the most important fragmentation in all but one case was C-N bond cleavage to form the NO2- ion. The spectra of the nonarom. alcs. contained a peak at [M + 46]-, and accurate mass measurements suggested the formal incorporation of NO2 into the mol. ion.

46)

Regio-, diastereo-, and enantioselective condensation of chiral vinylic borates with aldehydes.

Basile, Tiziana; Biondi, Stefano; Boldrini, Gian Paolo; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Perkin Transactions 1  1989, 1025-9.

Abstract

A regio- and diastereoselective synthesis of enantiomerically enriched syn-ketols I (R = Ph, hexyl, Et2CH) is reported, starting from homochiral 2-(but-2-en-2-yloxy)-1,3,2-dioxaborolanes II and III (R2 = e.g., CO2CHMe2) and RCHO.

45)

A new route to optically active (4R)-2-substituted 4-hydroxycyclopent-2-enones from D-glucose.

Mezzina, Elisabetta; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; UmaniRonchi, Achille.

Journal of the Chemical Society, Perkin Transactions 1  1989, 845-9.

Abstract

Cyclopentenones I (R1 = SiMe2CMe3, Me) were prepd. from tosylxylofuranuronic acid deriv. II in a series of reactions. The key step was the regioselective palladium-catalyzed alkylation of CH2(CO2Me)2 with furfuryl acetate III.

44)

Condensation of Reformatskii reagents with acetals in the presence of titanium tetrachloride. A novel entry to enantiomerically enriched b-hydroxy esters.

Basile, Tiziana; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Chemical Communications  1989, 596-7.

Abstract

3-Alkoxy esters are prepd. in high yield from the reaction BrZnCH2CO2Et (I) and acetals in the presence of TiCl4 under very mild conditions. Thus, treating (MeO)2CHPh with I/TiCl4 in CH2Cl2 gave 90% MeOCHPhCH2CO2Et. Using chiral acetals, the corresponding 3-hydroxy esters have been obtained in fair enantiomeric excess.

43)

New chirons from D-glucose. Regio- and diastereoselective carbon-carbon bond-forming reactions exploiting novel aldotetrofuranose acetates as chiral synthetic equivalents of tartaric aldehydes.

Dhavale, Dilip D.; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1989, 54, 4100-5.

Tetrofuranose acetates I (R = OAc) and II (R = b-OAc) were prepd. from diacetone D-glucose in parallel short routes.  They clearly act as chiral synthetic equiv. of D- and meso-tartaric aldehydes in Lewis acid-promoted reactions with S-based nucleophiles. The synthesis of immediate precursors, I and II (R = allyl, CH2COMe, CH2COPh) of 2-deoxy-L-hexoses is presented as an application.

41)

Synthesis of chiral homoallylic alcohols from aldehydes and diallyltin dibromide in the presence of monosodium (+)-diethyl tartrate.

Boga, Carla; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organometallic Chemistry  1988, 353, 177-83.

Abstract

The reaction of diallyltin dibromide, readily prepd. from allyl bromide and tin powder, with aldehydes in the presence of monosodium-(+)-diethyl tartrate affords the corresponding homoallylic alcs. in good yields with enantiomeric excesses in the range 42 to 71%. Thus, the reaction using BzH in THF at -55° afforded 65% (S)-PhCH(OH)CH2CH=CH2 in 71% e.e.

40)

Asymmetric aldol reactions using (4R-trans)-2-(1-methylethenyl)-1,3,2-dioxaborolane-4,5-dicarboxylic acid diethyl ester, a chiral precursor of the acetone enolate.

Boldrini, Gian Paolo; Lodi, Luisa; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organometallic Chemistry  1987, 336, 23-8.

Abstract

Oxidn. of title compd. I by Me3NO gives a chiral enol borate that condenses with aldehydes to give optically active 4-hydroxy-2-alkanones in 55-77% yield and 41-65% e.e.

39)

Synthesis of enantiomerically enriched homoallylic alcohols and of 1,2-dien-1-ols using chiral tin(IV) complexes containing diethyl tartrate as an auxiliary ligand.

Boldrini, Gian Paolo; Lodi, Luisa; Tagliavini, Emilio; Tarasco, Carmine; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1987, 52, 5447-52.

Abstract

R2C=CR1CH2Br (I; R = R1 = H; R = H, R1 = Me; R = H, R1 = EtO2C; R = Me, R1 = H) reacted with a complex prepd. from SnCl2 and (+)-EtO2CCH(ONa)CH(ONa)CO2Et and then R2CHO (R2 = cyclohexyl, Ph, Me3C, octyl, Me2C=CH) to give (S)- or (R)-R2C=CR1CH2CH(OH)R2 in 53-82% yield and 16-65% enantiomeric excess.  Use of this procedure with HC ºCCH2Br and R2CHO (R2 = Ph, cyclohexyl, octyl) gave 56-61% (S)- or (R)-CH2=C=CHCH(OH)R2 in 39-47% enantiomeric excess.  Reacting I (R = H, R1 = EtO2C) with PhCHO via the above procedure gave CH2=C(CO2Et)CH2CH(OH)Ph, which on treatment with NaH in THF gave 85% g-phenyl-a-methylene-g-butyrolactone.

38)

Planning organic syntheses. IV - Efficiency and profitability.

Trombini, Claudio.

Chimica e l'Industria (Milan, Italy)  1987, 69, 129-33.

Abstract

A review with 33 refs. on the questions of what constitutes a good process, a good intermediate, and a good strategy in org. synthesis.

37)

Planning organic syntheses. III.  Analysis of target skeletons.

Trombini, Claudio.

Chimica e l'Industria (Milan, Italy)  1987, 69, 99-104.

Abstract

A review with 100 refs.  Skeleton features such as rings and tertiary and quaternary centers are analyzed to det. criteria for singling out strategic disconnections.

36)

Planning organic syntheses. II. Analysis of target functionality.

Trombini, Claudio.

Chimica e l'Industria (Milan, Italy)  1987, 69, 82-6.

Abstract

A review with 100 refs.

35)

Planning organic syntheses. I. Synthetic plans and processes.

Trombini, Claudio.

Chimica e l'Industria (Milan, Italy)  1987, 69, 82-6.

Abstract

A review with 80 refs. on general aspects of a synthetic sequence and the classification of the synthetic processes.

34)

Palladium catalyzed allylation of Reformatskii reagents. Synthesis of g,d-unsaturated esters.

Boldrini, Gian Paolo; Mengoli, Marina; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Tetrahedron Letters  1986, 27, 4223-6.

Abstract

Reformatskii reagents, e.g., BrZnCH2CO2Et regioselectively react under mild conditions with allylic acetates, e.g., PrCH=CHCH2OAc in the presence of Pd(PPh3)4 to give g,d-unsatd. esters, e.g. PrCH=CHCH2CH2CO2Et in good yields.

33)

Nickel-catalyzed coupling of activated alkenes with organic halides.

Boldrini, G. P.; Savoia, D.; Tagliavini, E.; Trombini, C.; Ronchi, A. Umani.

Journal of Organometallic Chemistry  1986, 301, C62-C64.

Abstract

Alkenenickel complexes catalyzed the coupling of CH2=CHR (I, R = Ph, CO2Et) with aryl or vinyl halides.  Substitution or conjugate-addn. products were obtained depending on the activating group in I and on the nature of the org. halide.  Thus, to I (R = CO2Et), treated with NiCl2(Ph3P)2 and Zn in THF for 0.5 h, was added PhI to give 54% PhCH=CHCO2Et, 6% PhCH2CH2CO2Et, and 5% biphenyl.

32)

Prostanoids from D-glucose. Palladium-catalyzed alkylation of 1,2-O-isopropylidene-3-deoxy-5-acetoxy-a-D-erythro-pent-5-ene-furanose.

Capobianco, Massimo; Mezzina, Elisabetta; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Tetrahedron Letters  1986, 27, 1387-90.

Abstract

The erythro-pentenofuranose I (R = OAc) underwent Pd-catalyzed reaction with substituted acetic esters or PhSO2Na in the presence of Pd(0) catalyst to give I [R = CH(CO2Me)2, CH(CO2Et)2, CH(CN)CO2Me, CH(SO2Ph)CO2Et, PhSO2]. Decarbonylation gave I (R = CH2COMe, CH2CN, CH2SO2Ph). 

31)

A short route to 2-[6-(methoxycarbonyl)hexyl]-cyclopent-2-en-1-one.

Boga, Carla; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Synthesis  1986, 212-13.

The title prostaglandin intermediate I was prepd. by Grignard reaction of 2-(2-bromoethyl)-1,3-dioxolane with ClCO(CH2)7CO2Me, followed by hydrolysis in the presence of NaIO4 to give HCOCH2CH2CO(CH2)7CO 2Me which was cyclized with base to give I in 53% overall yield.

30)

Homoenantioselective synthesis of allylic alcohols from chiral allylic tin(IV) (+)-diethyl tartrate complexes and aldehydes.

Boldrini, Gian Paolo; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Chemical Communications  1986, 685-6.

Abstract

Optically active secondary homoallylic alcs. were prepd. by treatment of aldehydes with allylic Sn(IV) complexes contg. (+)-di-Et tartrate (I) as a chiral auxiliary ligand. Sequential treatment of I with NaH, SnCl2, CH2=CHCH2Br, and PhCHO in THF under an inert atm. at -5° for 10 min, 30 min, 5 h, and 17 h, resp., gave 82% (S)-HOCHPhCH2CH:CH2 in 62% enantiomeric excess.

29)

Application of potassium-graphite and metals dispersed on graphite in organic synthesis.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Pure and Applied Chemistry  1985, 57, 1887-96.

Abstract

A review with 21 refs., mainly of the authors' work. Potassium -graphite has been used as a heterogeneous reagent in several reactions, including the Birch-type reaction of a,b-unsatd. ketones and carboxylic acids and of Schiff's bases, the reductive cleavage of vinylic and allylic sulfones, the selective alkylation of aliph. esters, imines and nitriles, and the reductive decyanation of nitriles.  Potassium-graphite has also been exploited to prep. active metals, highly dispersed on the graphite surface (Met-Gr).  The active metals prepd. have found applications in Reformatsky reactions (Zn-Gr), prepns. of allylic organometallic species (Zn-Gr, Sn-Gr), reductive coupling of carbonyl compds. (Ti-Gr), debromination (Fe-Gr), vinylic and allylic substitution (Pd-Gr), and hydrogenation reactions (Pd-Gr, Ni-Gr).

28)

Synthesis of 2-(6-methoxycarbonylhexyl)cyclopent-2-en-1-one through acylation reactions of g-butyrolactone.

Boga, Carla; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Chemical Research, Synopses  1985, 226-7.

Enolization-lithiation of g-butyrolactone (I) followed by acylation with ClCO(CH2)7CO2Me (II) gave 52% lactone III. III was also prepd. in 68% yield by metalation of a-bromo-g-butyrolactone with Zn-graphite followed by treatment with II.  Hydrolysis-decarboxylation of III with Na2HPO4 in aq. dioxane followed by oxidn. with pyridinium chlorochromate gave HCO(CH2)2CO(CH2)7CO 2Me (IV). IV was also prepd. from I by O,C-bis(trimethylsilylation) followed by reaction with II and in situ hydrolysis-decarboxylation and oxidn. as before. On treatment with NaOMe in MeOH at room temp. IV cyclized to give the title compd. in 78% yield.

27)

Highly reactive metals from potassium-graphite. Preparation and use of titanium-graphite and tin-graphite.

Boldrini, Gian Paolo; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organometallic Chemistry  1985, 280, 307-12.

Abstract

The potassium-graphite route to active forms of metals has been extended to the prepn. of titanium-graphite (Ti-Gr) and tin-graphite (Sn-Gr).  The Ti-Gr is used to achieve the reductive coupling of ketones to give alkenes, and Sn-Gr is used in the prepn. of diallytin dibromide complexes which react with aldehydes to give homoallylic alcs.

26)

A new route to an active form of nickel.  Transfer hydrogenation of alkenes and carbonyl compounds with 2-propanol.

Boldrini, Gian Paolo; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1985, 50, 3082-6.

Abstract

A new procedure for the title reactions was developed using an activated form of metallic Ni prepd. by the thermal decompn. of Ni diisopropoxide in boiling 2-propanol.  Monosubstituted alkenes undergo C:C double-bond migration more quickly than redn.; the 2-alkene produced is then reduced to alkane.  Ketones are reduced in high yields, provided that the acetone formed during the process is removed continuously.  Unsatd. ketones are first converted to satd. ketones and then to alcs.  Thus, by careful control of the reaction course it is possible to stop the reaction at the first stage.  A comparison was made with the transfer hydrogenation of ketones catalyzed by alkali metal isopropoxides in 2-propanol.

1984-1980

Keywords:

heterogeneous reagents and catalysts (palladium, zinc, iron and nickel on graphite as reagents or catalysts in carbon-carbon bond forming reactions and in reduction reactions, potassium on alumina in metalation and reduction processes).

organic synthesis (lactones in organometallic reactions, the activating mobile phenylsulphonyl group, prostanoids, jasmonoids).

25)

Nucleophilic substitution reactions of allylic esters catalyzed by palladium-graphite and related heterogeneous catalysts.

Boldrini, Gian Paolo; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organometallic Chemistry  1984, 268, 97-106.

Abstract

Highly dispersed Pd on graphite, C or Al2O3 catalyzes nucleophilic substitution reactions of allylic esters with nucleophiles such as PhSO2-, (EtO2C)2CH- and 1-(1-cyclohexen-1-yl)pyrrolidine.  E.g., Pd dispersed on graphite catalyzes the substitution of CH2=CHCH2OR [R = Ac, P(O)(OEt)2, P(O)(OPh)2, CO2Me, CO2Ph] with PhSO2Na to give CH2=CHCH2SO2Ph.  The stereochem. and regiochem. of the reaction was discussed.

24)

Syntheses of hydroxy ketones from lactones.

Cavicchioli, Silvia; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1984, 49, 1246-51.

Abstract

g-Hydroxy ketones [e.g., BuCO(CH2)3OH] are cleanly obtained by the addn. of 1.1 equiv of BuLi to g-lactones dissolved in ether at -90°.  Under these conditions the formation of diols by double organometallic attack is avoided, esp. in the case of substituted lactones.  Similar reactions of d-valerolactone, e-caprolactone, and b-lactones gave complex mixts.  Furthermore the reactions of Grignard reagents with lactones in ether or in THF are quite poor.  The b-, d-, and e-hydroxy ketones are prepd. by cleaving the lactones with a,a-dilithioalkyl Ph sulfones in THF at low temps. to afford the w-hydroxy-b-keto sulfones, which are then cleaved with Al amalgam.

23)

Active metals from potassium-graphite. Zinc-graphite promoted synthesis of b-hydroxy esters, homoallylic alcohols and a-methylene-g-butyrolactones.

Boldrini, Gian Paolo; Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1983, 48, 4108-11.

Abstract

Active Zn on graphite, prepd. by redn. of anhyd. ZnCl2 with K-graphite in THF, was used conveniently for the prepn. of Reformatskii reagents and allylzinc bromides.  Condensation of organozinc derivs. with suitable carbonyl compds. affords improved yields of b-hydroxy esters, homoallylic alcs. and a-methylene-g-butyrolactones, relative to the known procedures.

22)

Active metals from potassium-graphite. Iron-graphite as a new debrominating agent of vic-dibromoalkanes and of a-bromo ketones.

Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1982, 47, 876-9.

Abstract

Iron-graphite (Fe-Gr), easily prepd. by redn. of FeCl3 with potassium-graphite (C8K) in THF, is conveniently used for the stereospecific debromination of vic-dibromoalkanes to alkenes and for the reductive debromination of a-bromo ketones to ketones in high yields.  The latter reaction proceeds via Fe(II) enolates, which undergo deuteration, condensation, or O-silylation by reaction with D2O, heptanal, or Me3SiCl, resp.  Reaction of a,a'-dibromo ketones with Fe-Gr leads to 2-oxyallyl cations which can be trapped by suitable electron-rich olefins (enamines) or dienes (furan).

21)

Cyclopentenones from g-lactones. Synthesis of 2-(6-carboxyhexyl)cyclopent-2-en-1-one, an intermediate in prostaglandin synthesis.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1982, 47, 564-6. 

Treating the a,a-dilithio deriv. of sulfone I with g-butyrolactone to give II was the key step in the prepn. of prostanoid synthon III.  The successive steps involved desulfonation, oxidn., and cyclization to give the protected alc. analog of III; deprotection and oxidn. to III were accomplished in a single step with Jones' reagent. 

20)

Active metals from potassium-graphite. Air-oxidized nickel-graphite as a new selective hydrogenation catalyst.

Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1981, 46, 5344-8.

Abstract

Air exposure of Ni-graphite affords a modified, less active hydrogenation catalyst, owing to a partial oxidn. of the metal, which is able to reduce C-C, C-O, and C-N multiple bonds under 30 atm of H at 30-130°. A remarkable bond selectivity in the hydrogenation of polyfunctional mols. such as unsatd. carbonyl compds. and b-diketones is obsd.

19)

Active metals from potassium-graphite. Highly dispersed nickel on graphite as a new catalyst for the stereospecific semihydrogenation of alkynes.

Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1981, 46, 5340-3.

Abstract

The redn. of bis(dimethoxyethane)dibromonickel by K-graphite affords highly dispersed Ni on the graphite surface (Ni-Gr1).  Freshly prepd. Ni-Gr1 is used in situ as a catalyst for semihydrogenation of alkynes to alkenes in the presence of ethylenediamine as catalyst modifier. Unconjugated and conjugated (Z)-alkenes with a stereospecificity of 96-9% and 94%, resp., are obtained.

18)

Active metals from potassium-graphite. Palladium-graphite-catalyzed vinylic substitution reactions.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille; Verardo, Giancarlo.

Journal of the Chemical Society, Chemical Communications  1981, 541-2.

Abstract

Pd-graphite, prepd. by redn. of PdCl2 with K-graphite in MeOCH2CH2OMe, catalyzed the stereospecific arylation or alkenylation of olefins by aryl, vinyl, or thienyl iodides.  E.g., treatment of CH2=CHCO2Et with PhI in the presence of Pd-graphite (Bu3N, 100°, 6 h, under Ar) gave 87% E-PhCH=CHCO2Et and with CH2=CH(CH2)4I gave 58% E,E-CH2=CH(CH2)4CH=CHCO2Et (14 h).

17)

Active metals from potassium-graphite. Palladium-graphite as catalyst in the hydrogenation of nitro compounds, alkenes, and alkynes.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille; Verardo, Giancarlo.

Journal of the Chemical Society, Chemical Communications  1981, 540-1.

Abstract

Pd-graphite, prepd. by redn. of PdCl2 with K-graphite in MeOCH2CH2OMe, effectively catalyzed the hydrogenation of arom. nitro compds., alkenes, and alkynes to anilines, alkanes, and (Z)-alkenes, resp.  E.g., hydrogenation of 3-MeC6H4NO2 with Pd-graphite (MeOH, room temp., 1 atm) gave 3-MeC6H4NH2 quant.; Me(CH2)7C ºCH gave 90% Me(CH2)7CH=CH2 and 6% n-C10H22, and PhC ºCPh gave 97% of a 94:6 mixt. of Z- and E-PhCH=CHPh and 2% PhCH2CH2Ph.

16)

Highly dispersed potassium on alumina as a metalating agent.  Alkylation of enolizable compounds.

Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organometallic Chemistry  1981, 204, 281-6.

Abstract

Highly dispersed K on Al2O3 acts as a metalating agent towards enolizable compds. and the intermediate organopotassium derivs. can be alkylated with primary alkyl bromides.  The reaction conditions are dependent on the substrate.  THF is the solvent of choice for the metalation of nitriles and aldehyde dimethylhydrazones at -60° and of N-cyclohexyl ketimines at room temp. whereas hexane must be used for ketones.

15)

Iron-graphite lamellar compounds prepared by chemical reduction of iron trichloride with potassium-graphite in tetrahydrofuran. Reply to comments.

Braga, Dario; Ripamonti, Alberto; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, DaltonTransactions  1981, 329-30.

Abstract

A polemic in reply to H. Schaefer-Stahl (ibid. 1981, 328). S.-S.'s failure to obtain Fe-graphite lamellar compds. was attributed to the crit. nature of the reaction conditions

14)

New routes to cis-jasmone and dihydrojasmone via 1,4-diketones exploiting the mobile activating sulfonyl group.

Mussatto, Maria Cristina; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry 1980, 45, 4002-5.

The diketo sulfones RCH(SO2Ph)COCH2CH2COMe [R = (Z)-CH2CH=CHEt, pentyl], obtained by reaction of PhSO2CRLi2 with g-valerolactone and Jones oxidn. of the resulting RCH(SO2Ph)COCH2CH2CHMeOH, were cleaved with Al amalgam in aq. THF to give the diketones MeCOCH2CH2COCH2R, which were then heated over alumina in benzene to give cis-jasmone and dihydrojasmone [I, R = (Z)-CH2CH=CHEt, pentyl], resp. 

13)

Reaction between 1,1-dilithioalkyl phenyl sulfones and w-bromo esters. Synthesis of cyclic vinyl ethers.

Mussatto, Maria Cristina; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Perkin Transactions 1  1980, 260-3.

Abstract

The reaction between PhSO2CRLi2 (I) (R = H, Et, n-heptyl) and Br(CH2)3CO2Et (-60°, THF) gave furylidene derivs. II (R = H, Et, n-heptyl) with minor amts. of the cyclopropyl ketones III (R = H, Et, n-heptyl).  A similar reaction of I (R = H) with Br(CH2)4CO2Et gave the cyclohexanone IV and the dihydropyran V.  Treatment of PhSO2CH2CO(CH2)4Br with base also gave a mixt. of IV and V. 

12)

Potassium on alumina as a reagent for reductive decyanation of alkylnitriles.

Savoia, Diego; Tagliavini, Emilio; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1980, 45, 3227-9.

Abstract

Highly dispersed K over neutral alumina, easily prepd. by melting K over alumina in an inert atm., effected reductive cleavage of the cyano group in alkylnitriles in hexane at room temp. in 70-91% yield.  This decyanation method was applied in the key step of a novel synthesis of (Z)-9-dodecen-1-yl acetate, the sex pheromone of Paralobesia viteana.

1979-1975

Keywords:

potassium-graphite as reagent for metalation and reduction reactions; formation of highly dispersed metals on graphite;

quaternary ammonium ylides , rearrangement of;

organomercury compounds, mass spectrometry of.

11)

Potassium-graphite as selective reducing agent for activated double bond systems.

Contento, Michele; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Synthesis 1979, 30-2.

A Birch-type redn. of a,b-unsatd. ketones, a,b-unsatd. carboxylic acids, Schiff bases, and PhCH=CHPh with C8K gave 57-92% the corresponding satd. compds.  Among 12 redns. so carried out were b-ionone to dihydro-b-ionone (77%), geranic acid to citronellic acid (91%), and PhCH=NCMe3 to PhCH2NHCMe3 (88%).

10)

Graphite lamellar compounds. Structure of transition metal intercalates.

Braga, Dario; Ripamonti, Alberto; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, DaltonTransactions  1979, 2026-8.

Abstract

The crystal structures of Ti, Mn, Fe, Co, Cu, and Zn graphite intercalates, prepd. from C8K and transition metal salts in THF, were detd. from x-ray diffraction data.  Lamellar compds. of stages 1-5 were formed with values of 0.56-0.58 nm for the thicknesses of the filled layers.  The introduction of the metal layers led approx. to the same increase in interlayer spacing for all stages.

9)

Graphite lamellar compounds.  A new route to transition metal intercalates.

Braga, Dario; Ripamonti, Alberto; Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Chemical Communications  (1978), 927-8.

Abstract

K graphite (C8K) reacted with Ti(OCHMe2)4, MnCl2.4H2O, FeCl3, CoCl2.6H2O, CuCl2.2H2O, and ZnCl2 in THF to give the corresponding intercalated metal graphite.  X-ray diffraction patterns showed the presence of different solid phases within the reaction products.

8)

Potassium-graphite as a metalation reagent. Synthesis of aldehydes and ketones by alkylation of imines and dihydro-1,3-oxazine.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of Organic Chemistry  1978, 43, 2907-10.

Abstract

Metalation of imines RCH2CR1=NR2 (R = H, alkyl, Ph; R1 = H, alkyl; R2 = cyclohexyl, tert-Bu) or the oxazine I with K-graphite and alkylation of the K salts with alkyl halides gave carbonyl compds. RCHR3COR1 and R2CH2CHO (R2 = alkyl).  The metalation reaction was shown to give enaminic anions. 

7)

Potassium-graphite (C8K) as a metalation reagent. Alkylation of nitriles and esters with alkyl halides under heterogeneous conditions.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Tetrahedron Letters  1977, 653-6.

C8K-catalyzed alkylation of nitriles and esters with alkyl halides gave mainly monoalkylated products. E.g., to a suspension of C8K in THF, PhCH2CN was added (-60°, under Ar) and stirred for 2 h.  BuBr was then added and the soln. warmed to 25°.  After 1 h, the mixt. was quenched to give, after workup, 67% PhCHBuCN.  The reaction occurs via carbanion intermediates, which may be trapped with aldehydes to give b-hydroxy nitriles or esters and the corresponding a ,b-unsatd. deriv.

6)

Selective alkylation of allyl phenyl sulfone. A novel synthesis of alk-2-enes.

Savoia, Diego; Trombini, Claudio; Umani-Ronchi, Achille.

Journal of the Chemical Society, Perkin Transactions 1  1977, 123-5.

Abstract

Treatment of the Li salt of PhSO2CH2CH=CH2 with alkyl halides gave PhSO2CHRCH=CH2 [I; R =  Bu, PhCH2, (CH2)nMe where n = 7, 15] as the major product, together with small amts. of PhSO2CR2CH=CH2 (II).  Isomerization of I [R = Bu, PhCH2, (CH2)nMe, n = 7, 15] with catalytic amts. of tert-BuOK gave E-PhSO2CR=CHMe (III).  A new simple method of reductive cleavage of the C-S bonds of compds. I-III with C8K is described, giving a general route to alk-2-enes.

5)

Mass spectra of saturated organomercurials.

Simonotti, L.; Trombini, C..

Inorganica Chimica Acta  1977, 21, L27-L28.

Abstract

Dialkylmercury compds.,R2Hg, (R = Me, Et, Pr, Bu, isobutyl, sec-butyl, and pentyl), were subjected to electron-impact and chem. ionization.  In the electron-impact spectrum of Me2Hg, the ions Me2Hg+, MeHg+, and CH3+ dominate.  In the 70 eV mass spectra of the other compds., Hg-free fragments predominate.  Lowering the ionization voltage to 20 and 15 eV causes the Hg-contg. fragments to become more important.  At 10 eV, mol. ions carry >95% of the total ion current.  In the chem. ionization studies, CH4, CH4/H2O, and isobutane were used as the reagents.  For CH4/H2O, the oxocations RHgOH2+ appear, probably originating in a 4-center reaction between hydronium ion and R2Hg.

4)

Quantitative analysis of organo-mercury compounds by mass spectrometry.

Casalini, Anna; Trombini, Claudio; Simonotti, Luca.

Annali di Chimica (Rome, Italy)  1976, 66, 67-72.

Abstract

A mass-spectrometric method is described for quant. and qual. detn. of ng levels of organomercury compds. such as diphenylmercury (I) [587-85-9].  The method identified both the metal and the rest of the mol. and is esp. useful in environmental pollutant studies.

3)

Gas-phase proton affinity: a measure of intrinsic basicity.

Trombini, Claudio; Bonafede, Sandra.

Annali di Chimica (Rome, Italy)  1976, 66, 19-39.

Abstract

A review, with 84 refs.

2)

Heterobenzyl quaternary ammonium salts. IV. 2-Thenyl group as terminus and migrating moiety in the Stevens and Sommelet rearrangements of a quaternary ammonium ion.

Giumanini, Angelo G.; Trombini, Claudio; Lercker, G.; Lepley, Arthur R.

Journal of Organic Chemistry  1976, 41, 2187-93.

Abstract

The band initiated rearrangement of I (X = Cl, iodo) gave II and III.  The kinetics indicated that IV was a common intermediate which was partitioned between the Stevens and Sommelet rearrangement routes.

1)

Heterobenzyl quaternary ammonium salts. V. Base-induced [1,2]- and [3,2]-rearrangements of N-(2-thenyl)-N-benzyldimethylammonium ion.

Giumanini, Angelo G.; Trombini, Claudio.

Journal für Praktische Chemie (Leipzig)  1975, 317, 897-906.

The title quaternary ammonium ion I underwent Sommelet and Stevens rearrangements induced by bases such as NaNH2, BuLi, or LiCH2SOMe. Ionization of the thenyl methylene group of I to give the corresponding thenyl ylide was the predominant process, yielding N-[1-(2-thienyl)-2-phenylethyl]dimethylamine and N-[a-(o-tolyl)-2-thenyl]dimethylamine. The strong tendency of the 2-thenyl ylides to produce relatively large amts. of the Sommelet amine was confirmed. Minor products are N-[2-(2-thienyl)-1-phenylethyl]dimethylamine and N-(a-phenyl-2-methyl-3-thienyl)dimethylamine derived from the alternate benzyl ylide.