Synthesis of Asymmetric Allenes with Chiral Copper Nucleophiles

Significance

Optically active allenes possessing axial chirality can be prepared through a 1,4-addition of nucleophiles to optically active propargylic acceptors. Herein, the authors illustrate an alternative route to these compounds. Organocuprates bearing a chiral sulfinyl auxiliary are added to propargylic electrophiles allowing for the formation of both axial chirality and a stereocenter. High diastereoselectivity is observed, and the yields indicate a complete kinetic resolution of the racemic propynylmesylates. Since the synthesis of enantiopure propargylic nucleophiles is challenging, this alternative strategy presents a useful route to asymmetric allenes.