Ruthenium tetroxide oxidation of N-alkyllactams.

Ruthenium tetroxide (RuO4) oxidation of N-alkyllactams proceeded regioselectively depending on the size of lactam ring, except for the seven-membered ring. Four- and eight-membered N-methyl- and N-ethyllactams were oxidized at the exocyclic α-carbon adjacent to nitrogen to produce the N-acyllactams and NH-lactams, while five- and six-membered lactams underwent endocyclic oxidation to yield the cyclic imides. Oxidation of seven-membered lactams yielded a mixture of products arising from both exocyclic and endocyclic oxidations. These regioselectivities were confirmed in the oxidation of substrates having a tertiary carbon at the oxidation position.