3H-azepines and related systems. Part 2. The photolyses of aryl azides bearing electron-withdrawing substituents
The photolyses of ortho-substituted aryl azides (o-XC6H4N3 where X = CONHNH2, CONHNCHAr, NO2, CN, CF3, SO2OMe, SO2NH2, or SO2Ph) in methanol–tetrahydrofuran solution are described. With X = CF3 or CONHNCHAr, 3-substituted 2-methoxy-3H-azepines are products, while in other cases polymeric products, amines, or mixtures of isomeric azepines are obtained. The product from the photolysis of o-azidophenyl phenyl sulphoxide (X = SOPh) is identified tentatively (n.m.r. evidence) as 7-methoxy-2-phenylsulphinyl-3H-azepine.
In contrast, methyl p-azidobenzoate and p-cyanophenyl azide yield the corresponding 5-substituted 2-methoxy-3H-azepines, whereas methyl m-azidobenzoate yields only methyl 2-methoxy-3H-azepine-6-carboxylate. Irradiation of methyl o-azidobenzoate in aqueous tetrahydrofuran gives 1,3-dihydro-3-methoxycarbonyl-2H-azepin-2-one.