Cyril Benhaim

Enantioselective Copper-Catalysed Conjugate Addition

The review covers the efforts made over the last decade towards designing efficient copper-catalysed systems for the asymmetric conjugate addition reaction.

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 conjugate addition to alkylidene malonates

Dialkylzinc and trialkylaluminium reagents undergo conjugate addition to alkylidene malonates with 0.5% copper triflate as catalyst. The reaction could be made enantioselective by completing the reaction in the presence of 0.5–1.0 mol% of chiral phosphorus ligand. Enantiomeric excesses (e.e.s) of up to 73% could be attained with a ligand prepared from TADDOL and 2-naphthylcyclohexanol.

Enantioselective Synthesis of β-Trifluoromethyl α-Amino Acids

We report herein the three-step enantioselective synthesis of beta-trifluoromethyl alpha-amino acids including trifluorovaline (TFV) using stereoselective hydrogenation with [((R)-trichickenfootphos)Rh(cod)]BF(4) catalyst as the key step.