Catalyst-Controlled Divergent C–H Functionalization of Unsymmetrical 2‑Aryl Cyclic 1,3-Dicarbonyl Compounds with Alkynes and Alkenes
2013-07-24T00:00:00Z (GMT) by
Achieving site-selective, switchable C–H functionalizations of substrates that contain several different types of reactive C–H bonds is an attractive objective to enable the generation of different products from the same starting materials. Herein, we demonstrate the divergent C–H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds that contain two distinct, nonadjacent sites for initial C–H functionalization, where product selectivity is achieved through catalyst control. By use of a palladium–N-heterocyclic carbene complex as the precatalyst, these substrates undergo oxidative annulation with alkynes to provide spiroindenes exclusively. In contrast, a ruthenium-based catalyst system gives benzopyrans as the major products. Examples of divergent, oxidative C–H alkenylations of the same substrates are also provided.