ASYMMETRIC CATALYSIS WITH CHIRAL COMPLEXES OF RHODIUM-O-ISOPROPYLIDENE-2,3-DIHYDROXY-1,4-BIS(DIPHENYLPHOSPHINO)-BUTANE .6. MECHANISM OF REDUCTION OF (E,Z)-ALPHA-ACYLAMINOCINNAMIC ACIDS WITH HOMOGENEOUS RHODIUM CATALYSTS

The stereochemistry of reduction of several α-acylaminocinnamic acids was investigated, in the presence of rhodium-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane (DIOP) catalyst. Cis addition on the Z isomer was demonstrated by using deuterium. Catalytic deuteration of the E isomer gives a mixture of diastereoisomers d2. This result was interpreted as an indication of some E-Z isomerization prior to reduction, allowing calculation of the actual optical yield. Tentative mechanisms for the E-Z isomerization which do not lead to d3 species are discussed. © 1978, American Chemical Society. All rights reserved.