Cycloadditions in syntheses. XXXII Intramolecular photocycloaddition of 4-(.OMEGA.-alkenyloxy)quinolin-2(1H)-one : Synthesis of 2-substituted cyclobuta[c]quinolin-3(4H)-ones.

Irradiation of 4-allyloxy-2-quinolone and 4- (pent-4-enyloxy) -2-quinolone gave corresponding cross and parallel adducts specifically, whereas 4- (but-3-enyloxy) -2-quinolone led to a mixture of cross and parallel adducts. Regioselectivity in these photoreactions was not affected by the introduction of substituents into 4- (ω-alkenyloxy) -2-quinolones.These cross adducts were transformed to 2-substituted 1, 2-dihydrocyclobuta [c] quinolin-3 (4H) -ones, whose synthesis could not be achieved by using so-far known intermolecular photocycloaddition of 4-alkoxy-2-quinolone to olefins (the Kaneko-Naito method). Preliminary experiments demonstrated that these 2-substituted derivatives could be used as synthons for 7, 8-disubstituted phenanthridin-6 (5H) -ones by an application of the benzocyclobutene method.