Highly Enantioselective Reactions of Configurationally Labile α-Thioorganolithiums Using Chiral Bis(oxazoline)s via Two Different Enantiodetermining Steps

Abstract

A cumene solution of α-stannyl benzyl phenyl sulfide was treated with n -BuLi and bis(oxazoline)- i Pr at −78 °C and subsequently with benzophenone to give the product with 99% ee. We confirmed that the reaction of α-lithio benzyl phenyl sulfide proceeds through a dynamic kinetic resolution pathway. The enantioselective reactions of α-lithio benzyl 2-pyridyl sulfide gave the products with stereochemistry reverse to that obtained in the reaction of benzyl phenyl sulfide. We confirmed that this reaction proceeds through a dynamic thermodynamic resolution pathway in which the reaction with an electrophile proceeds faster than interconversion between the diastereomeric complexes.