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 d^Fppe 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.