Singlet oxygen reactions of benzannelated isoquinolinones

Article abstract of DOI:10.1016/S0040-4020(98)01186-7

Tetraphenylporphin (TPP) or methylene blue (MB) sensitized photooxygenation reactions of benzannelated isoquinolinones 3 and 4 took place by initial attack of singlet oxygen on the enol etherenamine C=C double bond and proceeded via zwitterionic (10, 29) and endoperoxidic (11, 28, 30) intermediates. The product for 3 was 5 exclusively in MeCN, and 5 and the solvent trapping products 6 in MeOH. For 4, the products were 25 (and 26) in MeCN, while in MeOH, solvent trapping product 31 was also obtained for 4b. Intramolecular trapping of the zwitterionic intermediate during the singlet oxygen reaction of 4d to form 32 was also observed.