CINNOLINES .12. 1,3-DIPHENYL-2H-PYRROLO[3,4-C]CINNOLINE . STRUCTURE AND N-ETHYL DERIVATIVES

3,4-Dibenzylcinnoline is synthesised and oxidised with selenium dioxide to give 3,4-dibenzoylcinnoline and 3,4-dibenzylidene-3,4-dihydrocinnoline. 3,4-Dibenzoylcinnoline is identical with that obtained by the literature method - oxidation of 1 ,3-diphenyl-2H-pyrrolo[3,4-c]cinnoline. The assignment of the latter structure to the product from diazotisation and cyclisation of 3-amino-2,4,5-triphenylpyrrole is thus confirmed. The structures of two N-ethyl derivatives of the 1,3-diphenylpyrrolo[3,4-c]cinnoline system are established by chemical and spectroscopic methods.