Reactions of dimethoxycarbene with carbon–sulfur double bonds

Abstract

AbstractUnlike electrophilic carbenes, which react at sulfur to produce thiocarbonyl ylide intermediates, dimethoxycarbene (DMC), generated by thermolysis of an oxadiazoline at 110°C in benzene in a sealed tube, reacts at carbon, possibly to generate a zwitterionic intermediate, or at both carbon and sulfur in a concerted process that generates a thiirane. In case of the strained 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione (2), an assumed zwitterion undergoes ring expansion. In analogous reactions, unstrained thiones afford thiiranes, possibly by ring closure of the postulated intermediates or by concerted addition. Desulfurization of thiiranes, which occurs spontaneously in some instances, results in the formation of ketene acetals, many of which hydrolyze during workup. O‐Alkyl thioesters and xanthates react to afford products via insertion of the DMC into C—O or C—S bonds, respectively. Copyright © 2004 John Wiley & Sons, Ltd.