Synthesis of cyclic hydroxamic acids through -NOH insertion of ketones.

Treatment of cyclobutanone or cyclopentanone with N-hydroxybenzenesulfonamide under basic conditions yields the ring-expanded cyclic hydroxamic acid in 18-69% yield. Reactions of substituted cyclobutanones give ring expanded products where the -NOH group regio- and stereoselectively inserts to the more substituted position. This expansion likely proceeds through a mechanism that includes addition of the N-anion of N-hydroxybenzenesulfonamide to the ketone and a C-nitroso intermediate that rearranges to the final product.