The reaction of α-azidostyrene derivatives with hexacarbonylmolybdenum was found to give 2, 5-diarylpyrroles and acetophenone derivatives via a complexed 1-arylvinylnitrene intermediate, while that of 3-aryl-2H-azirines gave 2, 4-diarylpyrroles in addition to acetophenone derivatives and 2, 5-diarylpyrazines.