Gilbert Peiffer

Synthesis of water-soluble ligands with a quaternary ammonium salt: use in bdphasic palladium-catalyzed telomerisation of butadiene and isoprene

Abstract Water-soluble ligands are synthesized by quaternization of tertiary aminophosphine with either hydrochloric acid or methyl iodide. The use of these ligands in the biphasic palladium-catalyzed telomerisation of butadiene, produces 1-methoxy-2,7-octadiene with 78% selectivity and conversions ranging from 52 to 79%. Conversion and selectivity are little altered on catalyst recycling. Telomerisation of isoprene is somewhat less satisfactory, with a conversion not higher than 52%.

Characterization and synthesis of (−)-7-methoxydodec-4(E)-enoic acid, a novel fatty acid isolated from Lyngbya majuscula

Abstract The isolation and characterization of (−)-7-methoxydodec-4( E )-enoic acid, a novel fatty acid isolated from the marine Cyanophyte Lyngbya majuscula collected off the French Mediterranean coast are described. The synthesis of this acid and three of its isomers is reported.

Enantioselective synthesis of cyclic dialkyl (3-hydroxy-1-alkenyl) phosphonates by baker's yeast-mediated reduction of the corresponding enones

Abstract Cyclic dialkyl (3-oxo-1-cycloalkenyl) phosphonates were subjected to bakers yeast-mediated enantioselective reductions to afford the corresponding dialkyl (3-hydroxy-1-alkenyl) phosphonates. The six- and seven-membered ring enones were reduced with moderate to good enantiomeric excesses, whereas the five-membered ring substrate always yielded the double bond reduced compound. The use of different reduction conditions did not improve the ees markedly, but it was found, for the six-membered analogues, that the alkyl groups held by phosphorus influence dramatically the enantioselectivity of the reduction, leading to up to 95% enantiomeric excess.

Palladium catalysed allylic acetoxylation of dialkyl allyl phosphonates.

Abstract The catalytic acetoxylation of dialkyl allyl phosphonates with the Pd(OAc)2/benzoquinone/MnO2/HOAc system leads, regioselectively, to dialkyl 3- acetoxy 1-alkenyl phosphonates. On the basis of the regio- and stereoselectivity of the reaction, a mechanism is proposed which involves a (π-allyl) palladium complex as intermediate.

Synthèse de phosphinites dérivés de sucres : applications en cyclodimérisation du penta 2,4-diénoate de méthyle, en hydrogénation et en hydrosilylation de la pentolactone

Abstract Sugar-derived phosphinites, when used as ligands in the catalytic hydrogenation of α-ketopentolactone, lead to the corresponding alcohol with a better enantiomeric excess (20%) than in hydrosilylation (10%). In the cyclodimerisation of penta-2,4-dienoic acid methyl ester they lead to the meso cycloocta-3,7-diene-1,2-doic dimethyl ester.

Enzymatic resolution of diethyl (3-hydroxy-1-butenyl) phosphonate

The enzymatic esterification of diethyl (3-hydroxy-1-butenyl) phosphonate 1 with different enzymes has been carried out, and allows the preparation of (S)-1 and (R)-diethyl (3-acetoxy-1-butenyl) phosphonate 2 with very high enantiomeric excess. The absolute conguration of 1 was determined by independent synthesis from (S)-ethyl lactate.

Dimerisation de monoolefines catalysee par des complexes du nickel et du cobalt generes electrochimiquement

Abstract Dimerization of olefins was performed with NiL 2 X 2 and CoL 2 X 2 complexes by an electrochemical reduction process under controlled cathodic potential. The influence of several parameters (choice of anode, supporting electrolyte, ligand, temperature and pressure) was studied in order to increase the dimer production and selectivity. In the case of ethylene, with nickel-based catalysts, 2-butenes are formed selectively with a turn-over number of 12 000 within 50 h. With propylene as substrate methylpentenes are the main products, in which case the reaction rate appears to be two orders of magnitude lower than with ethylene under identical conditions. Although less active, cobalt-based catalysts show an unusual behaviour, as they are particularly selective for 1-butene production (> 90%).

Palladium-Catalyzed Acetoxylation of Cyclic Allyl Phosphonates in the Presence of Isopentyl Nitrite and Using Molecular Oxygen as Final Oxidant

Abstract The palladium-catalyzed acetoxylation of cyclic dialkyl allyl phosphonates is effected using palladium chloride as catalyst, in the presence of isopentyl nitrite in acetic acid under an oxygen atmosphere. The proposed mechanism for the reaction involves a palladium nitro–nitroso redox couple.

Etude de la dimerisation du propylene catalysee en phase homogene par des especes du type “HCoLx”

Abstract The dimerisation of propylene in methylpentenes (60%) at 25°C is catalysed by two active cobalt species. The first, HCoL 3 , issued from the system “Co(Acac) 3 /HAlEt 2 /L” in the presence of 1,5-cyclooctadiene, is more active (×30) and selective in 2-methyl-1-pentene (85% of dimers) than the second, formed from HCo(COD) 2 . Under low pressures of propylene (3 bar), the fraction of higher oligomers (mainly trimers) increases only up to 40%.

Synthese de ligands de type amino-diphosphinites; etude en RMN 13C et 31P. Application a la dimerisation du butadiene par les complexes du nickel

Abstract The new chiral aminodiphosphinite ligands are readily prepared from chiral amino acids. These compounds were characterized by 13 C and 31 P NMR spectroscopy and their behaviour as homogeneous catalysts was investigated in the linear dimerization of butadiene.