Highly Efficient and Markovnikov-Selective Cobalt Catalysis for the Construction of α‑Alkenylboronates

α-Alkenylboronates are appealing building blocks
in organic
synthesis, as well as promising monomers in polymerization. Herein,
we report a cobalt-catalyzed highly efficient Markovnikov-selective
hydroboration of terminal alkynes enabled by a recently developed
ligand to access α-alkenylboronates. This operationally simple
protocol not only exhibits good functional group tolerance but also
demonstrates compatibility with primary, secondary, and sterically
hindered tertiary aliphatic alkynes. Fourteen examples of gram-scale
reactions have been shown even with only 0.05 mol % catalyst loading
to deliver the corresponding products that could be easily purified
through distillation or recrystallization. Based on the control experiments,
the anti-interference ligand could inhibit the coordination
of boranes, improving the compatibility and regioselectivity of this
transformation.