Rhodium-Catalyzed Asymmetric C-H Insertion and Cyclopropanation

Significance

This first synthesis of a vinyldiazo­lactone lead to the discovery of its successful utility in rhodium-catalyzed asymmetric C-H insertion and cyclopropanation. Rh₂(S,R-MenthAZ)₄, a carboxamidate chiral rhodium catalyst, provided the highest ee and selectivity for C-H insertion using 1,4-cyclohexadiene. In contrast, vinylarenes undergo an efficient cyclopropanation under the same catalytic system with high yields and good diastereoselectivities. Reduction of the lactone and subsequent divinyl cyclopropane Cope rearrangement gives rapid access to hydroazulenes, seven-membered carbocycles that are present in many natural products.