Cobalt-Catalyzed Asymmetric Hydroboration/Cyclization of 1,6-Enynes with Pinacolborane

We report a cobalt-catalyzed asymmetric
hydroboration/cyclization
of 1,6-enynes with catalysts generated from Co­(acac)2 and
chiral bisphosphine ligands and activated in situ by reaction with
pinacol­borane (HBpin). A variety of oxygen-, nitrogen-, and
carbon-tethered 1,6-enynes underwent this asymmetric transformation,
yielding both alkyl- and vinyl-substituted boronate esters containing
chiral tetrahydrofuran, cyclopentane, and pyrrolidine moieties with
high to excellent enantio­selectivities (86%–99% ee).

本工作报道了一种钴催化的1,6-烯炔不对称氢硼化/环化反应：以Co(acac)₂与手性双膦配体原位生成催化剂，再经频哪醇硼烷（HBpin）原位活化。多种由氧、氮及碳链连接的1,6-烯炔均可发生该不对称转化，生成含有手性四氢呋喃、环戊烷及吡咯烷结构单元的烷基取代与乙烯基取代硼酸酯，产物对映选择性优异，范围为86%~99% ee。