9-Borabicyclo[3.3.1]nonane / 9-BBN

Sandra Forbes

Product Manager

9-Borabicyclo[3.3.1]nonane or 9-BBN is an organoborane compound. This colourless solid is used in organic chemistry as a hydroboration reagent. The compound exists as a hydride-bridged dimer, which easily cleaves in the presence of reducible substrates. 9-BBN is also known by its nickname 'banana borane'. This is because rather than drawing out the full structure, chemists often simply draw a banana shape with the bridging boron.

9-Borabicyclo[3.3.1]nonane is a mild reagent for the reduction of carbonyl compounds, acid chlorides and alkenes. As 9-BBN does not form complexes with tertiary amines, a stoichiometric amount of the reagent is sufficient for the complete reduction of amides to amines.

Recent Literature

Organoborane reductants have been rendered catalytic through an isodesmic B-O/B-H transborylation applied in the borane-catalyzed, chemoselective alkene reduction and formal hydrofunctionalization of enones. The reaction proceeds via a 1,4-hydroboration of the enone and B-O/B-H transborylation with HBpin, enabling catalyst turnover.

K. Nicholson, T. Langer, S. P. Thomas, Org. Lett., 2021, 23, 2498-2504. https://doi.org/10.1021/acs.orglett.1c00446

The combination of B2pin2 and KOtBu enables a chemoselective, metal-free reduction of aromatic nitro compounds to the corresponding amines in very good yields in isopropanol. The reaction tolerates various reducible functional groups.

H. Lu, Z. Geng, J. Li, D. Zou, Y. Wu, Y. Wu, Org. Lett., 2016, 18, 2774-2776. https://doi.org/10.1021/acs.orglett.6b01274

Quoted from: https://www.organic-chemistry.org/chemicals/reductions/9-borabicyclo[3.3.1]nonane-9-BBN.shtm

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