Silver-Catalyzed Regio- and Stereoselective Formal Carbene Insertion into Unstrained C-C σ-Bonds of 1,3-Dicarbonyls

A regio- and stereoselective silver-catalyzed formal carbene insertion into 1,3-dicarbonyls has been developed, using N-nosylhydrazones as diazo surrogates. Two new C-C bonds are constructed at the carbenic carbon center through the selective deavage of the C- C(=O) sigma-bond of acyclic 1,3-dicarbonyls, enabling the preparation of various synthetically useful polysubstituted gamma-diketones, gamma-ketoesters, and gamma-ketoamides in high yields. The in situ formation of a donor-acceptor cyclopropane, via reaction of the enolate of the 1,3-dicarbonyl with an electrophilic silver carbenoid, is proposed as a key process in the catalytic cycle.