Approaches to heterocyclic analogues of biphenylene. Part I. The reaction of 5,6-diaryl-2,3-dihydropyrazines with alcoholic alkali

2,3-Dihydro-5,6-diphenylpyrazine reacts with alcoholic alkali to form 2,3-diphenylpyrazine and 5,5′,6,6′-tetraphenyl-2,2′-bipyrazinyl, not 2,3,6,7-tetraphenyl-1,4,5,8-tetra-azabiphenylene. 2,3-Dihydro-5,6-bis-(p-methoxy-phenyl)pyrazine undergoes an analogous reaction, but 2,3-dihydro-5,6-bis-(p-nitrophenyl)pyrazine yields only an apparently polymeric material. The reaction of pp′-dinitrobibenzoyl with ethylenediamine produces not only 2,3-dihydro-5,6-bis-(p-nitrophenyl)pyrazine, but also NN′-bis-(p-nitrobenzoyl)ethylenediamine.