9-Borabicyclo[3.3.1]nonane or 9-BBN is an organoborane compound. This colourless solid is used in organic chemistry as a hydroborationreagent. The compound exists as a hydride-bridged dimer, which easily cleaves in the presence of reducible substrates.[1] 9-BBN is also known by its nickname 'banana borane'.[2] This is because rather than drawing out the full structure, chemists often simply draw a banana shape with the bridging boron.[3][better source needed]
Its highly regioselective addition on alkenes allows the preparation of terminal alcohols by subsequent oxidative cleavage with H2O2 in aqueous KOH. The steric demand of 9-BBN greatly suppresses the formation of the 2-substituted isomer compared to the use of borane.
^Soderquist, John A.; Brown, Herbert C. (1981). "Simple, remarkably efficient route to high purity, crystalline 9-borabicyclo[3.3.1]nonane (9-BBN) dimer". J. Org. Chem.46 (22): 4599–4600. doi:10.1021/jo00335a067.