Photochemistry of Oximes III. The Photochemical Beckmann Rearrangement

Cycloalkanone oximes of ring-size four to fifteen are shown to yield lactams upon irradiation in methanol solution. Acyclic ketoximes similarly yield Beckmann-type products in methanol solution. Unlike the Beckmann rearrangement, unsymmetrically α-substituted cyclohexanone oximes give mixtures of approximately equal parts of both possible lactam isomers. The photolysis of oximes epimeric at the α-carbon gives products in which the α-center has retained its configuration. The results are interpreted in terms of a concerted breakdown of an oxazirane intermediate.