Bridgehead Hydrazines. 2. Preparation and Photolysis of 2-Phenyl-s-triazolopyridazine-1,3-dione and of Pyridazinophthalazine-6,11-dione

Article abstract of DOI:10.1021/jo00350a034

The two title compounds 6 and 10 were prepared by Diels-Alder reactions of the appropriate cyclic azo compounds with butadiene followed by bromination and bisdehydrobromination.Photolysis of 6 in methanol resulted in 1,2- and 1,4-additions of the solvent to the dienic system and in (2 + 2) dimerization.Photolysis in dichloromethane resulted in rearrangement to a pyrrolo<1,2-a>triazine and in (2 + 2) dimerization.Photolysis of 10 was solvent independent and gave only (4 + 2) dimer.Mechanistic aspects of the photoreactions are discussed.