catecholborane

Catecholborane, often abbreviated HB(cat)2 or HBcat, is an organoborane reagent used in organic synthesis. It consists of a boron center bound to a single hydride and two catecholato ligands derived from catechol (1,2-dihydroxybenzene). The catechol rings chelate the boron, giving a neutral molecule that is relatively moisture-sensitive and typically handled under dry, inert conditions.

Preparation and handling

Catecholborane is generally prepared by reacting boron sources with catechol to form the HB(cat)2 complex. The compound is sufficiently stable for storage under appropriate dry conditions but reacts with water and air, so it is used and stored under inert atmosphere in most laboratory settings.

Applications and reactivity

The primary use of catecholborane is the hydroboration of alkenes and alkynes to give alkyl or vinyl boronates. After hydroboration, oxidation of the boronated intermediates with hydrogen peroxide in basic medium furnishes anti-Markovnikov alcohols. Catecholborane is valued for its moderate reactivity, selectivity, and compatibility with a range of functional groups. It is also employed in various reductions and in catalytic hydroboration systems where turnover is achieved with other catalysts or reagents.

Summary

As a versatile boron hydride, catecholborane provides a reliable route to hydroboration-derived products and to alcohols through oxidation, contributing to both straightforward and more nuanced transformations in synthetic organic chemistry.