Iterative Stereospecific Reagent-Controlled Homologation of Pinacol Boronates by Enantioenriched α-Chloroalkyllithium Reagents

Abstract

Reaction of pinacol boronates with putative enantioenriched α-chloroalkyllithium species, generated in situ from homochiral α-chloroalkylsulfoxides by sulfoxide ligand exchange with t-BuLi in PhMe at −78 °C, gave chain-extended boronic ester products with generally excellent stereochemical fidelity. Iteration of this stereospecific reagent-controlled homologation (StReCH) process enabled the programmed synthesis of all four stereoisomers of a stereodiad-containing model system (4-benzyl-1,6-diphenylhexan-2-ol) with er ≥ 97:3 in all cases.