Photoinduced molecular transformations. Part 159. Formation of some furonaphthyridinones by selective β-scission of cyclobutanoxyl radicals generated from [2 + 2] photoadducts of 4-hydroxy-1-phenyl[1,8]naphthyridin-2(1H)-one with alkenes

Article abstract of DOI:10.1016/0040-4020(96)00210-4

The [2 + 2] photoaddition of 4-hydroxy-1-phenyl[1,8]naphthyridin-2(1H)-one 7 with various alkenes in methanol gave regioselectively the corresponding head-to-tail adducts (8, 9, and 11). The photolysis of the hypoiodites generated by the in situ reaction of the cyclobutanol adducts 8, 9, and 11 with excess mercury(II) oxide-iodine reagent in benzene induced a regioselective scission of their non-ring junction bond of the corresponding alkoxyl radicals to give substituted 3,9-dihydro-9-phenylfuro[2,3-b][1,8]naphthyridin-4(2H)-one (12 and 15) and/or substituted 3,5-dihydro-5-phenylfuro[3,2-c][1,8]naphthyridin-4-(2H)-one (13, 14, and 16). An unusual byproduct 12a was formed in the photolysis of hypoiodite of the [2 + 2] photoadduct 8a of 4-hydroxy-1-phenyl[1,8]naphthyridin-2-(1H)-one with isobutene.