organoboranes

Organoboranes are organoboron compounds that contain a covalent carbon–boron bond. The class includes alkyl-, aryl-, and alkenylboranes as well as boronic acids (RB(OH)2) and boronate esters (RB(OR')2), and broader organoboron reagents used in organic synthesis. Their versatility stems from the reactivity of the C–B bond, which can be converted into a wide range of C–C and C–heteroatom bonds, making them central reagents in organic synthesis.

Most organoboranes are prepared by hydroboration of alkenes or alkynes using borane reagents such as BH3·THF, catecholborane, or 9-borabicyclo[3.3.1]nonane (BBN). They can also be formed by catalytic C–H borylation or transmetalation. For practical handling, boronic acids and their esters (particularly pinacol boronate esters) are widely used because of improved stability and easy purification.

Key transformations include hydroboration-oxidation of alkenes to anti-Markovnikov alcohols, with subsequent oxidation (H2O2/NaOH). Suzuki-Miyaura cross-coupling uses organoboron reagents with palladium catalysts and base to form C–C bonds with aryl or vinyl partners; this reaction tolerates many functional groups and is a staple in medicinal chemistry and materials science. Other processes involve electrophile coupling, Matteson-type homologations, and various borylation strategies that introduce or transform C–B bonds.

Organoboranes are generally valued for their chemoselectivity, mild conditions, and compatibility with a broad range of substrates. While boronic acids are moisture sensitive, boronate esters such as RB(pin) are typically stable and widely used in industry. The field remains essential for contemporary synthetic methods and the construction of complex molecules.