Photoinduced Molecular Transformations. 128. Regioselective Photocycloaddition of 3-Acetoxyquinolin-2(1H)-one with Alkenes and Formation of Furoquinolin-4(5H)-ones, 1-Benzazocine-2,3-diones, and Cyclopropabenzazepine-2,3-diones via a β-Scission of Cyclobutanoxyl ...

Article abstract of DOI:10.1021/jo00028a037

We have found that <2 + 2>? photoadducts can be obtained by the photoaddition of 3-acetoxyquinolin-2(1H)-one with acyclic and cyclic alkenes.The photoaddition of 3-acetoxy-2-quinolin-2(1H)-one with 2-methylpropene, 2,3-dimethyl-2-butene, and 2-methoxypropene thus afforded regioselective head-to-tail adducts in 59-97percent yields.The photoaddition of 3-acetoxy-2-quinolin-2(1H)-one with cyclopentene and cyclohexene resulted in the formation of sterically disfavored cis-cisoid-cis photoadducts as the major products, with the accompanying formation of cis-transoid-cis photoadducts as the minor products in combined yields of 87 and 66percent, respectively.The photolysis of the hypoiodites generated in situ from cyclobutanols derived from all of the photoadducts induced β-scissions at the outer bonds of the corresponding cyclobutanoxyl radicals to give furo<2,3-c>quinolin-4(5H)-ones in 15-50percent yields with an accompanying formation of 7- and 8-membered lactams arising from β-scissions at the catacondensed bonds of the cyclobutanoxyl radicals in 2-62percent yields.The molecular structure of one of the novel 7-membered lactams that successively fused with cyclopropane and cyclopentane rings was established to be trans-5,8,9,10,10a,10b-hexahydro-5-methylcyclopenta<3,4>cyclopropa<1,2-d>benzazepine-6,7-dione by X-ray crystallographic analysis.The pathways leading to the formation of all of these products arising from β-scissions are discussed.