Stephane Rosset

Synthesis and Application of Chiral Phosphorus Ligands Derived from TADDOL for the Asymmetric Conjugate Addition of Diethyl Zinc to Enones

Asymmetric conjugate addition of diethylzinc to cyclohexen-2-one, chalcone, and benzalacetone has been found to occur with 0.5% copper(II) triflate and 1% chiral phosphite. Cyclic phosphites derived from TADDOL gave excellent to moderate enantiomeric excesses. The nature of the exocyclic substituent of the dioxaphospholane ring is important, but the chiral induction is imposed by the TADDOL framework. Syntheses of all the TADDOL ligands are described.

Asymmetric synthesis of ibuprofen via diastereoselective alkylation of a homochiral N-acylbornanesultam

A very short, 4 step synthesis of 2-(4-isobutylphenyl)propionic acid (ibuprofen) was achieved in 57% overall yield, using a highly diastereoselective alkylation of the chiral enolate derived from N-(4-isobutylphenyl)acetyl bornanesultam as a key step.

New P-chiral polyfluoroalkyl phosphorodiamidite ligand in asymmetric transformations catalyzed by palladium and copper complexes

Chiral phosphorus-containing ligands having polyfloroalkyl substituents may be used for the preparation of metal complex catalysts which could be recycled via phase separation [1]. Following the approach proposed by us previously [2], we synthesized a new P-chiral polyfluoroalkyl phosphorodiamidite L as shown in Scheme 1. The product was stable on storage and readily soluble in organic solvents. It was tested as chiral auxiliary in palladium-catalyzed enantioselective amination of 1,3-diphenylprop-2-en-1-yl acetate (I) with dipropylamine according to the procedure described in [3] (Scheme 2). In all experiments, a steadily high enantioselectivity level was reached (ee 91– 95%), regardless of the L/Pd molar ratio (1 : 1 or 2 : 1) and reaction medium. However, the substrate conversion turned out to be quite sensitive to the solvent nature: it did not exceed 32% in tetrahydrofuran but was almost complete in methylene chloride.