Asymmetric Henry Reaction Catalyzed by C2-Symmetric Tridentate Bis(oxazoline) and Bis(thiazoline) Complexes: Metal-Controlled Reversal of Enantioselectivity

Dynamic kinetic asymmetric transformations of β-stereogenic α-ketoesters by direct aldolization

Dynamic kinetic asymmetric transformations (DyKAT) of racemic β-bromo-α-keto esters by direct aldolization of nitromethane and acetone provide access to fully substituted α-glycolic acid derivatives bearing a β-stereocenter. The aldol adducts are obtained in excellent yield with high relative and absolute stereocontrol under mild reaction conditions. Mechanistic studies determined that the reactions proceed through a facile catalyst-mediated racemization of the β-bromo-α-keto esters under a DyKAT Type I manifold.

Organocatalytic asymmetric Michael addition of 5H-oxazol-4-ones to nitroolefins

The first organocatalytic asymmetric Michael addition of 5H-oxazol-4-ones to nitroolefins has been developed. In the presence of easily prepared L-tert-leucine-derived tertiary amine/thiourea catalyst, the Michael addition of 5H-oxazol-4-ones to nitroolefins proceeded in an excellent diastereo- and enantioselective manner (up to 99% ee and >19:1 dr). The Michael adducts obtained are valuable precursors for the synthesis of chiral α-alkyl-α-hydroxy carboxylic acid derivatives, which represent a series of versatile building blocks in many biologically active compounds.

Enantioselective synthesis of α-oxy amides via Umpolung amide synthesis

α-Oxy amides are prepared through enantioselective synthesis using a sequence beginning with a Henry addition of bromonitromethane to aldehydes and finishing with Umpolung Amide Synthesis (UmAS). Key to high enantioselection is the finding that ortho-iodo benzoic acid salts of the chiral copper(II) bis(oxazoline) catalyst deliver both diastereomers of the Henry adduct with high enantiomeric excess, homochiral at the oxygen-bearing carbon. Overall, this approach to α-oxy amides provides an innovative complement to alternatives that focus almost entirely on the enantioselective synthesis of α-oxy carboxylic acids.

Asymmetric synthesis of an antagonist of neurokinin receptors: SSR 241586

SSR 241586 is a 2,2-disubstituted morpholine, developed by Sanofi-Aventis, which is active in the treatment of schizophrenia and irritable bowel syndrome (IBS). Different strategies have been studied to synthesize this molecule and among the strategies an organo-catalyzed Henry reaction, applied to an α-keto ester, has produced SSR 241586 in excellent enantiomeric excess.