Gérard Buono

Lipase-catalyzed ester formation in organic solvents an easy preparative resolution α-substituted cyclohexanols

Abstract The commercial preparation “lipase My” catalyses ester formation from an alcohol and a fatty acid in organic solvents. Preparative resolution of α-substituted cyclohexanols, including menthol, was achieved under these conditions.

Lipase catalyzed reactions and strategy for alcohol resolution

Abstract Asymmetric hydrolysis, ester interchange and ester formation were carried out for menthol resolution with Candida cylindracea lipase. The reactions were realized under emulsified conditions with water soluble enzyme and in organic medium with an insoluble enzyme preparation. In the latter case, an enhancement of the enantioselectivity uas observed. The potentialities of ester interchange and ester formation for preparative alcohol resolutions are discussed.

Lipase-catalyzed reactions in organic media: competition and applications

Lipases (triacylglycerol acylhydrolase, EC 3.1.1.3) have been used in organic media for the catalysis of reactions such as hydrolysis, esterification and transesterification. In these conditions it was confirmed that all reactions proceed through an acyl enzyme intermediate in two successive steps: acyl enzyme formation and solvolysis. The competition between two acyl acceptors (acyl donors) for reaction with a donor (acceptor) is described for the first time. A kinetic model is proposed using a competitive factor which is in good accordance with experimental results. The model was used successfully for the prediction of alcohol (acid) separations and resolutions by lipases.

Design of a new class of chiral quinoline–phosphine ligands. Synthesis and application in asymmetric catalysis

Abstract The design and synthesis of a new class of chiral quinoline–phosphine ligands has been achieved. Their efficiency as asymmetric ligands in enantioselective palladium-catalyzed allylic substitution reactions and in the asymmetric copper-catalyzed addition of diethylzinc to enones was also investigated.

Use of alkaloids and aminoalcohols in catalytic asymmetric induction:Temperature effect on the addition of diethylzinc to benzaldehyde

Abstract A surprising effect of temperature on enantiomeric excess in the stereospecific addition of diethylzinc to benzaldehyde with alkaloids as catalysts is reported, as well as the induction of chirality by some commercial aminoalcohols as catalysts in the same reaction.

Enantioselective trimethylsilylcyanation of aromatic aldehydes catalyzed by titanium alkoxide–chiral o-hydroxyarylphosphine oxides complexes

Abstract A series of new chiral titanium alkoxide– o -hydroxyarylphosphine oxides complexes has been used as catalysts in the asymmetric trimethylsilylcyanation of aromatic aldehydes. The corresponding cyanohydrins have been obtained in high chemical yields with good to excellent enantiomeric excesses up to 98%. The influence of the structural features of the catalysts on the enantioselectivity has been investigated.

Synthese d'aminophosphinephosphinites chiraux. Utilisation en reduction asymetrique catalytique

Abstract The chiral aminophosphinephosphinites ligands (AMPP) are directly synthesized from natural amino alcohols or by reduction of formyl esters of α-amino acids and PPh2Cl. Their cationic rhodium complexes have been found to be excellent catalysts for enantioselective hydrogenation of dehydroamino acids (ee ∼ 86%, yield ∼ 100%) for example. Asymmetric reduction of ketones can also be performed with the new alkyl AMPP* modified rhodium catalyst (ee 50%).

ENANTIOSELECTIVE PALLADIUM CATALYZED ALLYLIC SUBSTITUTION WITH NEW CHIRAL PYRIDINE-PHOSPHINE LIGANDS

Abstract The synthesis of new chiral pyridine-phosphine ligands 1–3 was achieved and assessed in the enantioselective palladium catalyzed allylic substitution of 1,3-diphenyl-2-propenyl acetate 4 with dimethylmalonate 5 . Enantioselectivities up to 87% were obtained.

Enantioselective formation of quaternary centers on β-ketoesters with chiral palladium QUIPHOS catalyst

Abstract Asymmetric formation of quaternary centers by allylic alkylation of β-ketoesters using the chiral palladium QUIPHOS catalyst has been achieved. The results obtained not only depend on the reaction conditions but also on the structural features of both β-ketoesters and allylating agents. Enantiomeric excesses of up to 95% have been observed.

New chiral o-hydroxyphenyl diazaphospholidine oxide. Catalytic application in asymmetric addition of diethylzinc to aromatic aldehydes

Abstract Synthesis of diastereomerically pure o-hydroxyphenyl diazaphospholidine oxide 2 was achieved from a chiral diamine derived from (S)-proline. This new compound has been tested as catalyst in the asymmetric addition of diethylzinc to aromatic aldehydes. Corresponding sec-alcohols were obtained in high yields (up to 90%) with enantiomeric excesses varying from 15 to >99%. The influence of the solvent and also the important relation existing between the nature of the aldehydes and the enantioselectivity have been investigated.