Thermal rearrangements of 2,3-diphenyl-2H-azirine

Abstract

Heating 2,3-diphenyl-2H-azirine in a sealed tube at 250 °C for 3 h yields 2-phenylindole, 2,3,4,5-tetraphenylpyrrole, 2,4,5-triphenylimidazole, and 1-benzyl-2,4,5-triphenylimidazole as major products, with tetraphenylpyrazine, tetraphenylpyrimidine, pentaphenylpyridine, benzonitrile, benzamide, and stilbene being produced in smaller yield. In an attempt to elucidate the reaction pathways, it was shown that benzonitrile is not an intermediate, that the reaction between tetraphenylpyrrole and phenylcarbene yields pentaphenylpyridine, and that a similar reaction with 2,4,5-triphenylimidazole produces 1-benzyl-2,4,5-triphenylimidazole, tetraphenylpyrazine, and tetraphenylpyrimidine.