Solid State Photochemistry: Absolute Asymmetric Pnotocyclization of an Achiral S-Aryl o-Benzoylbenzotfaioate to an Optically Active Phthalide Involving a Novel Phenyl Migration

摘要

Photoreactions in the solid phase often present unusual and interesting behavior because of the restrictions to molecular motions that are imposed by the environment. Prochiral reactions that occur under the influence of chiral crystalline media ate among the most interesting examples of solid state control, and several successful "absolute" asymmetric syntheses involving unimoleculai reactions have been reported. In this Communication we report an example involving chiral crystals of an achiral S-(o-tolyl) o-benzoylbenzothioate which gives an optically active phthalide via a novel photochemical 1,4-phenyl migration. The proposed reaction mechanism was revealed in this case by a stereochemical correlation based on the absolute configuration of the starting thioester and the final photoproduct.