COBALT-CATALYZED HYDROFUNCTIONALIZATION/CYCLIZATION OF UNSATURATED HYDROCARBONS

Abstract

Our research focused on cobalt catalyzed hydrofunctionlization/cyclization transformations of unsaturated hydrocarbons. Firstly, we reported that cobalt catalysts in combination with phosphine ligands showed good reactivity in hydrosilylation of terminal alkynes with high regio- and stereoselectivity. Additionally, excellent chemoselectivity to alkyne was also observed when double bond and triple bond are in the same substrate. Unlike cobalt pincer complexes, our cobalt/phosphine catalytic system can be in stu activated by silanes without any external activators. Then we made a study of internal allene hydroboration. Our studies strongly suggest the mechanism predominantly favors Co-Bpin intermediate. With the knowledge of cobalt catalyst in promoting hydrofunctionalization of unsaturated hydrocarbons, we extend the catalytic system to hydroboration/cyclization of 1,7-enynes, constructing chiral cyclic compounds. To our delight, a series of chiral quinolinones containing quaternary stereogenic centers at 3-carbon were obtained. The borylated quinolines can be readily converted into a variety of compounds with chiral six-member ring structure.