Benzonitrile N-(phthalimido)imide, a functionalised 1,3-dipole. Preparation of 4,5,8-triphenylpyridazino[4,5-d]triazine and generation of 3,6-diphenyl-4,5-didehydropyridazine

Abstract

5-Phenyl-2-phthalimidotetrazole (1) has been prepared and shown to react readily with cyclohexene, dimethyl acetylenedicarboxylate, and dibenzoylacetylene, to give the cycloadducts of the functionalised 1,3-dipole, benzonitrile N-(phthalimido)imide (2). The adduct formed with dibenzoylacetylene, 4,5-dibenzoyl-3-phenyl-1-phthalimidopyrazole (5), has been converted into 4,5,8-triphenylpyridazino[4,5-d]triazine (8). This triazine undergoes thermal fragmentation to give diphenylbutadiyne, 3,6-diphenyl-4,5-didehydropyridazine being proposed as an intermediate. An alternative route to 3,6-diphenyl-4,5-didehydropyridazine is described which involves the preparation and oxidation of 1-amino-4,7-diphenyltriazolo[4,5-d]pyridazine (11).