Intermolecular Photochemical Cycloaddition of 4-Methoxy-2-quinolone with Olefins : A Regioselective Synthesis of 5-Substituted Cyclobuta [c]-2-quinolones

Abstract

Irradiation of 4-methoxy-2-quinolone (IV) in methanol in the presence of substituted ethylenes provided intermolecular addition products. The cycloaddition reaction was shown to be regioselective giving in all cases 5-substituted 3, 6-dihydrocyclobuta [c]-2-quinolones (V). Base treatment of these cycloadducts afforded the corresponding cyclobuta [c]-2-quinolones (VI).