Reactions of trichloroacetyl isothiocyanate with organic azides

Abstract

Benzyl azide reacts with trichloroacetyl isothiocyanate to give 7a in chloroform solution, and 11 in acetone solution. These 1,2,4‐oxathiazolidines were characterized by 13C nmr spectroscopy (Scheme 2), but could not be isolated since they deteriorated via the carbodiimide 8a into the 1,2,4‐thiadiazolidine 9a. The oxathiazoline 6a is assumed as an intermediate and was trapped by isocyanates and dicyclohexylcarbodiimide to give the 1,2,4‐thiadiazolidines 10a,b and 12 respectively. Isopropyl azide also reacts with trichloroacetyl isothiocyanate to give the labile oxathiazolidine 7b, which decomposes to the carbodiimide 8b and the 1,2,4‐thiadiazolidine 9b. In the case of diphenylmethyl azide, however, no evidence was obtained for the presence of the oxathiazolidine 7c in the 1H nmr spectra; only the carbodiimide 8c was observed. A mechanistic rationalization is presented in Scheme 1.