Synthesis of Enantiomerically Pure Bicyclo[4.2.0]octanes by Cu-Catalyzed [2+2] Photocycloaddition and Enantiotopos-Differentiating Ring Opening

摘要

The wide distribution of bicyclo[4.2.0]octanes in natural products and the inherently difficult synthesis of strained cyclobutanes renders the synthesis of compounds with the general framework A (Scheme 1) a challenging task.Quite clearly,the cyclobutane part invites a photochemical key step,and [2+2] photocycloaddition reactions with cyclohexenones have been studied intensively.In these examples enantiomerically pure products have always been obtained from enantiomerically pure starting materials.