Reactions of 5-chloro-1,2,3-thiadiazolium salts with activated methylene compounds

Abstract

The N-3 and N-2 methylated 1,2,3-thiadiazolium tetrafluoroborates 3 and 4 react with aliphatic activated methylene ketones and esters in the presence of a base to give the substitution products 7–11 and 18–24. Under similar conditions activated methylene azoles afford products formulated by NMR analysis as N–S ⋯ O rotamers (25, 26), N–S ⋯ N rotamers (12–15, 27–29), or a mixture of both (16, 17, 30). The X-ray crystal structure analysis of product 21, derived from the thiadiazolium salt 4 and 2,2-dimethyl-1, 3-dioxane-4, 6-dione, reveals a nearly linear N–S ⋯ O sequence (169°) and a short S ⋯ O contact (2.37/2.34 Å) for the two independent molecules.