Aspects of stereochemistry. Part XXIII. Configuration of some 2,4-disubstituted derivatives of 1,3-dioxolan

Abstract

Chemical evidence is provided which proves the correctness of the configurations previously assigned to cis- and trans-4-substituted derivatives of 2-phenyl-1,3-dioxolan based on the magnitude of the chemical shift of the benzyl protons in the n.m.r. spectra. Treatment of 2-O-benzylglycerol with N-bromosuccinimide affords cis-4-hydroxymethyl-2-phenyl-1,3-dioxolan, whereas the 1-O-benzyl ether is converted into a mixture of the cis- and the trans-form of 5-hydroxy-2-phenyl-1,3-dioxan and 4-hydroxymethyl-2-phenyl-1,3-dioxolan. A mechanism for the stereospecificity of the former reaction is presented.