Ring-Enlargement of in Situ Generated Cyclopropanones with Carbonyls and Imines: Synthesis of γ-Butyrolactones and -lactams

We report a ring-enlargement of in situ generated cyclopropanones with aldehydes, ketones, and aldimines to access γ-butyrolactones and γ-lactams. Using bench-stable 1-sulfonylcyclopropanols as cyclopropanone precursors, the reaction proceeds under mild conditions and affords the products in yields of up to 84% across a range of carbonyl and imine coupling partners. Mechanistic experiments and DFT studies provide insight into the reaction pathway.