Organostannanes Derived from (−)-Menthol: Controlling Stereochemistry during the Preparation of (1R,2S,5R)-Menthyldiphenyltin Hydride and Bis((1R,2S,5R)-menthyl)phenyltin Hydride

Reaction of (1R,2S,5R)-menthylmagnesium chloride (MenMgCl) with triphenyltin chloride in THF proceeds with epimerization of the C-1 carbon of the menthyl group and results in a mixture of (1R,2S,5R)-menthyltriphenyltin (1) and (1S,2S,5R)-menthyltriphenyltin (2). Addition of Lewis bases such as triphenylphosphine to the THF solution of triphenyltin chloride prior to addition of the Grignard reagent suppresses epimerization and enables isolation...