The hydroboration reaction and transformations of its organoborane products are described. The mechanism and the chemo‐, regio‐, and stereoselectivity of the hydroboration reaction are presented, as well as the synthesis and characteristics of the most common hydroborating agents. Transformations of organoboranes may involve carbon‐hetero atom bond formation and lead to stereoselective synthesis of organic halides, amines, aziridines, sulfur, selenium, and mercury compounds. Hydroboration‐protonolysis is a nonocatalytic method of cis‐hydrogenation of multiple bonds. Hydroboration‐oxidation is a standard method for cis‐anti‐Markovnikov hydroxylation of multiple bonds.
Carbon‐carbon bond formation can be accomplished by transformation of organoboranes through coupling of groups attached to boron, cross‐coupling of organoboranes with organic halides, organoborate rearrangements providing access to alkynes, (
E
)‐ and (
Z
)‐alkenes, (
E,E
)‐, (
E,Z
)‐, (
Z,Z
)‐dienes, and enynes. Single‐carbon insertion reactions include carbonylation, cyanidation, and the DCME and related reactions. Other reactions include α‐ and β‐alkylation of carbonyl compounds, the addition of alkynyl, alkenyl, and allylic boranes to aldehydes, leading to proparylic alcohols and stereodefined allylic and homoallylic alcohols, boron‐stabilized carbanions, the boron Wittig reaction, and concerted reactions of allylic and vinylic boranes. Contrathermodynamic isomerization of olefins is discussed. The synthesis of boron‐containing polymers and of isotopically labeled compounds is covered. Asymmetric synthesis via chiral organoboranes is covered in detail.