Copper‐Catalyzed Markovnikov Hydroboration of Alkenes via Hydrogen Atom Transfer (MHAT)

The synthesis of organoboron compounds is continually improving due to their relevance as intermediates in the construction of diverse fine chemicals. Among the different strategies used, direct hydroboration of alkenes remains the most direct and atom‐economical, with a large part of recent efforts focused on catalysts based on the more abundant and less toxic first‐row transition metals. Herein, we present a protocol for the copper‐catalyzed Markovnikov hydroboration of alkenes under mild reaction conditions, requiring only stoichiometric amounts of a simple and commercially available borane (pinacolborane). Remarkably, beyond its advantages in catalytic activity, this system proceeds through a new radical pathway for catalytic hydroborations, encompassing two subsequent hydrogen atom transfer processes: one that activates the borane and forms the copper hydride (HAT) and another that activates the alkene (MHAT).