Pinacolborane

Pinacolborane, commonly abbreviated HBPin, is an organoboron compound in which boron bears a terminal hydride and is bound to the pinacolato ligand, derived from pinacol (2,3-dimethyl-2,3-butanediol). The B–O(pin) bonds stabilize the boron center, giving a relatively stable boron-hydride reagent for use in organic synthesis. It is typically handled under inert atmosphere and is moisture sensitive.

Pinacolborane is a widely used hydroboration reagent. In hydroboration reactions, HBPin adds across carbon–carbon multiple bonds to furnish alkyl or vinyl boronates (R–BPin or vinyl-BPin). Under various transition-metal catalysts (for example copper, rhodium, or others), hydroboration can be carried out with high regio- and, in some cases, stereoselectivity. Oxidative workup of the resulting boronates converts them to alcohols, providing anti-Markovnikov alcohol products from alkenes. Beyond hydroboration, HBPin serves as a boron source in a range of functionalization reactions and can be used to prepare diverse organoboron compounds via subsequent transformations, including cross-coupling.

Preparation and availability: HBPin is commercially available and can be prepared by established routes involving pinacol and borane transesterification or hydroboration. It is often used as a solution in inert solvents and stored under inert atmosphere.

Safety: As a boron-hydrogen reagent, HBPin should be handled with appropriate precautions, avoiding inhalation, ingestion, and moisture; workups should be performed under proper lab safety conditions.

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