DOUBLE-TRAPPING OF TRIPLET BIRADICALS IN THE CLEAVAGE OF SPIROPYRANS AND SPIROOXAZINES

Saturation with nitric oxide, NO, of oxygen-free benzene solutions of some nitrospiro-[indoline-pyrans], spiro[indoline-naphthoxazine] and spiro[indoline-pyridobenzoxazine] led to double-trapping of biradicals. The resulting species have been detected by means of EPR spectroscopy and identified as 7-membered cyclic alkyl alkoxy nitroxides on the basis of their spectral parameters. The process, which takes place in the daylight and is not affected by UV irradiation, was not observed in spiropyrans not containing the indoline moiety.