Flash vacuum pyrolysis of N -alkenylbenzotriazoles and N -alkenylisoxazolones

The flash vacuum pyrolysis of 1-(2-ethoxycarbonylethenyl)benzotriazole has been reinvestigated, and the processes leading to the formation of ethyl indole-3-carboxylate and 2-ethoxyquinolin-4(1 H )-one elucidated. Similar pathways are followed in the flash vacuum pyrolysis of the corresponding benzisoxazolone. Some N -ethenylisoxazolones have been pyrolysed to form pyrroles, but rearrangement of the intermediate carbenes may be observed. Photolysis of the isoxazolones gives carbenes that may be captured by solvent or give pyrroles.