Journal of heterocyclic chemistry vol:29 issue:1 pages:17-23
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 C-13 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 H-1 nmr spectra; only the carbodiimide Bc was observed. A mechanistic rationalization is presented in Scheme 1.