Conical intersections and photoreactions of 2H-azirines Original Research Article

CASSCF calculations were performed on the nπ*- and ππ*-excited states of 2H-azirine as well as some alkyl-substituted 2H-azirines. An S1/S0 conical intersection (CI) was located, through which a direct formation of nitrile ylide can occur. In addition, an S2/S1 CI was found, from which a barrierless reaction path leads to nitrene in the S1-excited state.