Kinetic Resolution of a-Silyl-Substituted Allylboronate Esters via Chemo- and Stereoselective Allylboration of Aldehydes

Abstract

We describe the kinetic resolution of alpha-silyl-substituted allylboronate esters via chiral phosphoric acid-catalyzed chemo-, diastereo- and enantioselective allylboration of aldehydes. This process provides two synthetically versatile enantioenriched compounds, (Z)-delta-silyl-substituted anti-homoallylic alcohols and alpha-silyl-substituted allylboronate esters, with a selectivity factor up to 328. We propose that the reaction proceeds through a closed chair-like transition state with the silane moiety occupying a pseudo-axial position, thus readily resolving alpha-silyl-substituted allylboronate esters. The synthetic utility of the obtained enantioenriched compounds is highlighted by their further transformations to give a diverse set of enantioenriched molecules.