Trapping of photochemical intermediates as a tool in organic synthesis. Preparation of spiroaziridinopyridones, a new heterocyclic system

Whereas alkyl lithium and Grignard reagents both at rt and at −80°C thermally react with 3-methylisoxazolo[5,4-b]pyridine giving alkylation and/or isoxazole ring opening products, sodium malonate and sodium boron hydride react only under UV irradiation. Selective trappings of ketenimine or azirine intermediates give an enaminopyridone or two diasteroisomeric spiroaziridinopirydones. Regioselective opening of the aziridine ring with perchloric acid gives 3(1-amino-ethyl)-1H-pyridin-2-one.