Nucleophilic substitution of acyl chlorides by electrogenerated polysulfide ions in N,N-dimethylacetamide

Abstract

The reactions between acyl chlorides RC(O)Cl (a) [R = Me (1), Prⁱ (2), Bu^t (3), Ph(4)] and electrogenerated S₃^˙- (⇌ S₆^2- ) ions have been investigated in N,N-dimethylacetamide by spectroelectrochemistry. With R = alkyl, thiocarboxylate ions and sulfur resulting from the fast initial substitutions cause partial formation of both acyl disulfide ions and diacyl disulfides (b) at a y ratio [RC(O)Cl]/[S₃^˙-] of 0.5; the second step stoichiometrically (y = 1) affords diacyl disulfides 1b–4b as the presumed products. The formation of these species only is confirmed on a preparative scale from two sets of experiments: (i) direction addition of acyl chlorides (1a–4a) to chemically generated S^⅓- solutions; (ii) electrolysis of sulfur in the presence of acyl chlorides 2a–4a.