A comparison of some pyrolysis reactions of benzotriazoles, benzisoxazolones and benzisothiazolones

The products of flash vacuum pyrolysis of N-acetyl, N-methyl, N-benzyl and N-heteroaryl-substituted benzotriazole, 2,1-benzoxazol-3-one and 2,1-benzothiazol-3-one have been compared. The pyrolysis of benzotriazoles and benzisoxazolones appears to involve an iminocarbene intermediate, although the N-benzyl analogues react by radical pathways. Benzisothiazolones appear to form iminoketene intermediates.