Synthesis of Complex Tertiary Glycolates by Enantioconvergent Arylation of Stereochemically Labile α‑Keto Esters

Enantioconvergent
arylation reactions of boronic acids and racemic
β-stereogenic α-keto esters have been developed. The reactions
are catalyzed by a chiral (diene)­Rh­(I) complex and provide a wide
array of β-stereogenic tertiary aryl glycolate derivatives with
high levels of diastereo- and enantioselectivity. Racemization studies
employing a series of sterically differentiated tertiary amines suggest
that the steric nature of the amine base additive exerts a significant
influence on the rate of substrate racemization.