Exo-Selective Reductive Macrocyclization of Ynals
journal contributionposted on 20.03.2015, 00:00 by Hengbin Wang, Solymar Negretti, Allison R. Knauff, John Montgomery
A general protocol for the highly exo-selective macrocyclization of ynals using a nickel/N-heterocyclic carbene catalyst system has been developed. A series of 10- to 21-membered macrocycles bearing an exomethylene substituent was synthesized in good yields with excellent regioselectivity (exo/endo >95:5). Very high levels of long-range diastereocontrol can also be achieved for some classes of macrocycles. Complementary to previously reported endo-selective macrocyclizations, this method provides accesses to exoalkylidene macrocycles from simple ynals in high selectivity.