Ligand-Enabled Chemo- and Regioselective Ir(I)-Catalyzed Intermolecular Hydrocarbonation of Allenes: Access to Branched Products with All-Carbon Quaternary Centers

Abstract

An iridium complex featuring the perfluorinated bisphosphine ligand dFppe can catalyze intermolecular hydrocarbonation reactions of allenes with precise control over the selectivity to yield highly valuable branched products instead of the more common linear derivatives. Using N-substituted 3-carboxamide pyrroles as C─H donors, the reaction gives exclusively C-4 substituted products, while furan analogues yield C-2 substituted derivatives. β-Unsubstituted acrylamides can also be used as C─H sources to give chiral skipped dienes. The additions are equally efficient using monosubstituted and 1,1-disubstituted allenes, enabling the efficient formation of products bearing tertiary and all-carbon quaternary stereocenters. Moreover, a preliminary analysis with chiral bisphosphinite ligands confirms the feasibility of an enantioselective variant. Computational (DFT) studies provide relevant insights into this remarkable ligand-driven branched selectivity.