Jean-Michel Brunel

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.

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.

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.

Chiral o-hydroxyarylphosphine oxides: a new family of efficient catalysts in asymmetric addition of diethylzinc to benzaldehyde

Abstract A serial of new chiral o-hydroxyarylphosphine oxides has been used as catalysts (5 mol%) in the asymmetric addition of diethylzinc to benzaldehyde. 1-Phenylpropanol is obtained in high chemical yields with good to excellent enantiomeric excesses up to 98%. The influence of the structural features on the enantioselectivity has been investigated.

Enantioselective borane reduction of ketones catalysed by a chiral oxazaphospholidine-borane complex

The chiral oxazaphospholidine–borane complex 2 was used as catalyst (2 mol %) in asymmetric reduction of ketones by borane with an enantioselectivity ranging from 33 to 92% at 110 °C and 100% conversion; under stoichiometric conditions the reduction proceeded with 99% enantiomeric excess.

Mechanistic investigation into the addition of diethylzinc to aromatic aldehydes catalyzed by chiral o-hydroxyaryldiazaphosphonamides

Abstract A mechanistic investigation into the addition of diethylzinc to aromatic aldehydes catalyzed by chiral o -hydroxyaryldiazaphosphonamides is described. A positive non-linear effect has been encountered and the X-ray structure of catalyst anti - 1 has been realized.

Synthesis of new chiral σ2λ2-phosphenium cations

The synthesis of two new chiral σ2λ2-phosphenium cations 3 and 9 bearing proximal methoxy groups and their corresponding phosphine-borane adducts is reported. Phosphenium 9 has been successfully used in a chelotropic cycloaddition reaction with 2,3-dimethyl butadiene leading to the formation of a new σ4λ4-adduct.

Enantioselective rhodium catalyzed hydroboration of olefins using chiral bis(aminophosphine) ligands

Abstract The synthesis of new chiral bis(aminophosphine) ligands 1–5 was achieved and assessed in the enantioselective rhodium catalyzed hydroboration of various olefins with catecholborane. Enantioselectivities up to 77% were obtained.

Enzymatic desymmetrization of prochiral 2,3-bis(acetoxymethyl)bicyclo[2.2.1]hepta-2,5-diene and 2,3-bis(hydroxymethyl)bicyclo[2.2.1]hepta-2,5-diene

Abstract Enzymatic desymmetrization of the title compound 1 is reported using various commercially available lipases in hydrolysis and alcoholysis reactions or ester synthesis. In this area, lipase Amano AK ( Pseudomonas sp.) proved to be the best lipase whatever the experimental conditions used. The monoacetate product 2 is indifferently obtained with more than 95% enantiomeric excess (ee) as the levorotatory enantiomer 2a or the dextrorotatory one 2b .

Recent advances in asymmetric copper allylic oxidation of olefins

Abstract This review deals with the recent advances in asymmetric copper allylic oxidation of olefins. An exhaustive analysis of the results has been realized showing the limitation of the different asymmetric catalytic systems used.