Silylative Kinetic Resolution of Acyclic Secondary Benzylic Alcohols Catalyzed by Chiral Guanidine Having Axial Chirality Containing a Methoxy Group

Abstract

New chiral guanidine catalysts having axial chirality containing a methoxy group were synthesized. Subsequently, their catalytic ability was examined by applying the silylative kinetic resolution of racemic alcohols using chlorosilanes. Based on an X-ray crystallographic analysis of the catalysts, the functional role of the methoxy group was predicted, and the plausible reaction pathways and a transition state were described. It was also revealed that the existence of hydrogen bonding between the methoxy group on the catalyst and hydrogen atom at C-1 position of the substrates was of great importance for attaining high selectivity and reactivity. The proposed method is applicable to various acyclic aryl, heteroaryl, and normal-alkyl alcohols exhibiting medium to high s-values (s = 15–96, 15 examples).