Interaction of the isomeric chlorosulphonylbenzoyl chlorides and benzene, under the influence of aluminium chloride

Abstract

Acylation rather than sulphonylation is the major primary reaction when the isomeric chlorosulphonylbenzoyl chlorides (I) are stirred with aluminium chloride (1 or 2 mol. equiv.) and benzene at room temperature. The ortho-isomer (I) also yielded o-benzoylbenzenesulphinic acid (V) and chlorobenzene by reduction of the first-formed o-benzoylbenzenesulphonyl chloride. When ethylene dichloride is used as solvent, sulphonylation is almost completely inhibited and there is no reduction of the ortho-isomer. This provides a convenient synthesis for o-, p-, and the previously unknown m-benzoylbenzenesulphonyl chlorides. Electron-attracting groups in the nucleus of benzenesulphonyl chloride retard sulphonylation whereas the same substituents in benzoyl chloride accelerate acylation.