Nitrile sulphides. Part 1. 1,3-Dipolar cycloaddition to carbonyl groups activated by trihaloalkyl substituents; synthesis and crystal structure of 1,3,4-oxathiazoles

Abstract

Nitrile sulphides, generated by the thermal decarboxylation of 1,3,4-oxathiazol-2-ones, undergo 1,3-dipolar cycloaddition to the carbonyl group in chloral, hexachloroacetone and α,α,α-trifluoroacetophenone to yield 2,2,5-trisubstituted 1,3,4-oxathiazoles (18–76%). Characterisation of the products is based on analytical and spectrosopic evidence, and is confirmed for 5-phenyl-2-trichloromethyl-1,3,4-oxathiazole and 5-(p-methoxyphenyl)-2-phenyl-2-trifluoromethyl-1,3,4-oxathiazole by X-ray crystal structure analyses. The oxathiazole rings are planar, with a localised CN double bond.