Synthesis and Tautomeric Structure of the Azo-Coupling Products of 2-Methyl-7-Phenylpyrimido[1,2-b][1,2,4]triazepine-4,9(3H,5H)-dione

Abstract

A simple synthetic strategy is described for synthesis of 3-arylazo-2-methyl-7-phenylpyrimido[1,2- b][1,2,4]triazepine-4,9-diones 4a–j. The acid dissociation constants were determined for the series prepared and were correlated by a Hammett-type equation using enhanced substituent constants. The results of such correlation together with the spectral data, including 15N isotopic labelling, indicated that the studied compounds exist predominantly in the hydrazone tautomeric form.