Photochemistry of 3-amino-1,2-benzisoxazole: unexpected photoisomerization of an amino-spiro-2H-azirine to a 1H-diazirine

UV irradiation of 3-amino-1,2-benzisoxazole isolated in an argon matrix leads to the formation of an amino-spiro-2H-azirine. The amino-spiro-2H-azirine was found to photoisomerize back to 3-amino-1,2-benzisoxazole and also to a 1H-diazirine, which isomerizes to a carbodiimide. All the reported species were characterized experimentally by IR spectroscopy and confirmed by comparison with theoretical IR spectra. The discovery of the transformation of an amino-spiro-2H-azirine into a 1H-diazirine is unprecedented in the chemistry of reactive intermediates.