Photo-induced formation of cyclopropanols from α-ketoamides via γ-C-H bond activation

A novel type of photocyclization of α-ketoamides was developed, affording unique cyclopropanols bearing amide functionality. N-tert-Butyl, N-trityl, or N-non-substituted α-ketoamides with a bulky substituent at the β-position of the amide functionality were efficiently converted to corresponding cyclopropanols through the activation of the γ-C-H bond followed by C-C bond formation between the α- and γ-positions of the amide. Hydrogen abstraction from the γ-position of the amide was considered to be the rate-determining step of cyclopropanol formation, based on the kinetic isotope effect. Cyclopropanols could be converted to two different types of functionalized α-ketoamides depending on the method of ring-opening.