Zur Photodimerisierung von 3‐Phenyl‐2 H ‐azirinen . Vorläufige Mitteilung

Irradiation of 3‐phenyl‐2 H ‐azirine ( 2 ) in benzene solution with a high‐pressure mercury lamp yields 4,5‐diphenyl‐1,3‐diazabicyclo[3,1,0]hex‐3‐ene ( 4 ) and not 3‐phenylimino‐4‐phenyl‐1‐azabicyclo[2,1,0]pentane ( 1 ), as had been reported previously by others [2]. 2‐Methyl‐3‐phenyl‐2 H ‐azirine ( 3 ) yields on irradiation a 2:1 mixture of 2‐ exo , 6‐ exo ‐ and 2‐ exdo , 6‐ exo ‐dimethyl‐4,5‐diphenyl‐1,3‐diazabicyclo[3,1,0]hex‐3‐ene (2‐ exo ,6‐ exo ‐ and 2‐ endo , 6‐ exo ‐ 5 ). Irradiation of 2,3‐diphenyl‐2 H ‐azirine ( 8 ) leads to the formation of 2,4,5‐triphenyl‐imidazole ( 9 ) and tetra‐phenylpyrazine ( 10 ). The suggested reaction path for the generation of 9 and 10 is shown in Scheme 2.