Intramolecular Insertions into Unactivated C(sp³)-H Bonds by Oxidatively Generated β-Diketone-α-Gold Carbenes: Synthesis of Cyclopentanones.

Generation of reactive α-oxo gold carbene intermediates via gold-catalyzed oxidation of alkynes has become an increasing versatile strategy of replacing hazardous diazo carbonyl compounds with benign and readily available alkynes in the development of efficient synthetic methods. However, one of the hallmarks of metal carbene/carbenoid chemistry, i.e., insertion into an unactivated C(sp(3))-H bond, has not be realized. This study reveals for the first time that this highly valuable transformation can be readily realized intramolecularly by oxidatively generated β-diketone-α-gold carbenes using ynones as substrates. Substrate conformation control via the Thorpe-Ingold effect is the key design feature that enables generally good to excellent efficiencies, and synthetically versatile cyclopentanones including spiro-, bridged, and fused bicyclic ones can be readily accessed.