Organosulphur compounds. Part VIII. Reaction of monothiocarboxylic acids with dicyclohexylcarbodi-imide and other reactions leading to monothio-anhydrides

Abstract

The reaction of monothiocarboxylic acids with dicyclohexylcarbodi-imide affords diacyl sulphides and dicyclohexylthiourea. In some cases the formation of N-acyl-NN′-dicyclohexylthioureas was observed. Diacyl sulphides were also obtained by treatment of O-trimethylsilyl thiocarboxylates with acyl chlorides. The mechanism of diacyl sulphide formation in both reactions is discussed. The reaction of thioacyl chlorides with salts and silyl esters of carboxylic acids gives the unstable unsymmetrical monothioanhydrides, which disproportionate to yield carboxylic anhydrides and unidentified sulphur-containing products. The mass spectral characteristics of diacyl sulphides and O-trimethylsilyl thiocarboxylates are reported.