Enantioselective Rhodium‐Catalyzed Pauson–Khand Reactions of 1,6‐Chloroenynes with 1,1‐Disubstituted Olefins

摘要

Abstract An enantioselective rhodium(I)‐catalyzed Pauson–Khand reaction (PKR) using 1,6‐chloroenynes that contain challenging 1,1‐disubstituted olefins is described. In contrast to the previous studies with these types of substrates, which are only suitable for a single type of tether and alkyne substituent, the new approach results in a more expansive substrate scope, including carbon and heteroatom tethers with polar and non‐polar substituents on the alkene. DFT calculations provide critical insight into the role of the halide, which pre‐polarizes the alkyne to lower the barrier for metallacycle formation and provides the proper steric profile to promote a favorable enantiodetermining interaction between substrate and chiral diphosphine ligand. Hence, the chloroalkyne enables the efficient and enantioselective PKR with 1,6‐enynes that contain challenging 1,1‐disubstituted olefins, thereby representing a new paradigm for enantioselective reactions involving 1,6‐enynes.