Enantio- and Regioselective CuH-Catalyzed Conjugate Reduction of Yne–Allenones

A new asymmetric catalytic conjugate reduction of yne–allenones to synthesize enantioenriched cyclobuta­[a]­naphthalen-4­(2H)-ones has been established that uses copper–bisphosphine complexes as catalysts and gives excellent regio- and enantioselectivities (≥99% ee) in most cases. This protocol tolerates a broad scope of substrates, exhibits high compatibility with various substituents, and gives excellent stereoselectivity, providing a catalytic and efficient entry to fabrication of synthetically important chiral 6–6–4 tricarbocyclic scaffolds.