Addition reactions of heterocyclic compounds. Part L. Reactions of 1-alkylbenzotriazoles and benzo[c]cinnolines with dimethyl acetylenedicarboxylate

Abstract

1-Alkylbenzotriazoles add 2 molecular proportions of dimethyl acetylenedicarboxylate, forming pyridazino[1,2-a]-benzotriazoles, which with acid undergo ring scission and an alternative cyclisation to form pyridazino[2,3-a]-quinoxalinones. Benzo[c]cinnolines add 2 molecular proportions of the dimethyl ester across the 5,6-double bond, but reaction with the diethyl ester in ethanol gives products involving this solvent. The n.m.r. spectra of benzo[c]cinnoline and some pyridazinobenzotriazoles have been computer-simulated.