Asymmetric induction in copper (I)-catalyzed intramolecular [2 + 2] photocycloaddition: Synthesis of enantiopure cyclobutane derivatives

Abstract

A simple approach for asymmetric induction in copper (I)-catalyzed intramolecular [2 + 2] photocycloaddition of 1,6-dienes, where asymmetric catalysis or chiral auxiliaries have been inefficient, has been developed using the concept of chirality transfer from the readily available 2,3-di-O-cyclohexylidine–(<i style="">R</i>)-(+)-glyceraldehyde to produce enantiopure oxa-bicyclo[3.2.0]heptane derivatives. A novel anion-induced cleavage of the tetrahydrofuran ring in these oxa-bicyclo[3.2.0]heptane derivatives has led to a convenient access to the synthetically useful <i style="">cis</i>-1,2-disubstituted cyclobutanes in enantiomerically pure form.