Abstract

Tautomerism of 2,1,3-benzothiadiazinone 2,2-dioxide and other related fused heterocyclic amides has been studied by means of experimental (H-1- and C-13-NMR) and theoretical (ab initio calculations) techniques. The synthesis and spectroscopic characterization of mono- and di-blocked derivatives was carried out. The results predict that the keto form is the most abundant tautomer in the gas phase, while the N1(H) hydroxy is the preferred one in solution and the solid state. (C) 1999 Elsevier Science Ltd. All rights reserved.