Z or E enolate geometry is the primary determinant of diastereoselectivity in the aldol reaction. Although amide and thioamide enolates are anticipated to have predominantly the E geometry because of the intrinsic steric demand, spectroscopic confirmation of the geometry in solution has remained elusive, particularly in the realm of highly stereoselective catalytic asymmetric aldol reactions. Herein
The reaction of RhCl(PPh3)(3) with Et2Zn easily generated a rhodium-hydride complex (Rh-H) that added to alpha,beta-unsaturated esters to form rhodium enolate complexes by formal 1,4-reduction. These rhodium enolates gave the corresponding Reformatslcy-type reagents through transmetalation, and they reacted with various aldehydes and ketones to give reductive aldol-type products in good to excellent yields. (C) 2013 Elsevier Ltd. All rights reserved.