Acylation. Part XXXIII. The spontaneous and acid-catalysed acylation of thiols by dimethylketen in diethyl ether

Abstract

At 25°, in diethyl ether solution, ethanethiol and 1,1-dimethylethanethiol add spontaneously to dimethylketen at rates comparable with those found for their oxygen analogues. The observed rates are very irreproducible, but the only product is the expected thio ester. Experiments with added radicals suggests that a radical path may contribute to these spontaneous thiolyses.

The addition of ethanethiol is catalysed by isobutyric acid. This reaction is analogous to acid-catalysed addition of alcohols, and is of the first order in keten, thiol, and catalyst. Similar catalysis of the addition of 1,1-dimethylethanethiol is not detectable owing to its slowness and to the preferential addition of the catalyst.