Enantioselective Conia-Ene-Type Cyclizations of Alkynyl Ketones through Cooperative Action of B(C6F5)3, N-Alkylamine and a Zn-Based Catalyst

An efficient and highly enantioselective Conia-ene-type process has been developed. Reactions are catalyzed by a combination of B(C6F5)(3), an N-alkylamine and a BOX-ZnI2 complex. Specifically, through cooperative action of B(C6F5)(3) and amine, ketones with poorly acidic alpha-C-H bonds can be converted in situ to the corresponding enolates. Subsequent enantioselective cyclization involving a BOX-ZnI2-activated alkyne leads to the formation of various cyclopentenes in up to 99% yield and 99:1 er.