NHC Ligand-Enabled, Palladium-Catalyzed Non-Directed C(sp³)–H Carbonylation To Access Indanone Cores

Abstract

A palladium-catalyzed C(sp3)–H carbonylation of alkylated aryl triflates or bromides under 1 atm of CO has been developed, in which no directing group or oxidant was required. The essence of this reaction is the combination of appropriate NHC ligands with palladium to facilitate the formation of the five-membered cyclopalladium intermediate. Mechanism studies suggest that the insertion of carbon monoxide into two five-membered cyclopalladium species generated via palladium migration might be the crucial step for this transformation. This method offers an efficient solution for expedient construction of indanone cores, which are valuable synthons and pharmacophores ubiquitously found in numerous natural products.