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Further Information

Related Reactions
Fleming-Tamao Oxidation
Markovnikov's Rule
Synthesis of Alcohols
Synthesis of Boranes

Brown Hydroboration

The syn-addition of hydroboranes to alkenes occurs with predictable selectivity, wherein the boron adds preferentially to the least hindered carbon. This selectivity is enhanced if sterically demanding boranes are used.

Coupling the hydroboration with a subsequent oxidation of the new formed borane yields anti-Markovnikov alcohols. The hydroboration/oxidation sequence constitutes a powerful method for the regio- and stereoselective synthesis of alcohols.

The product boranes may also be used as starting materials for other reactions, such as Suzuki Couplings (see Recent Literature).

Mechanism of the Brown Hydroboration

The selectivity of the first addition of borane can be relatively low:

The subsequent additions are more selective as the steric bulk increases, and anti-Markovnikov selectivity predominates in the end:

Oxidation with hydrogen peroxide leads to alcohols:

Sterically demanding boranes offer enhanced selectivity. One example of a sterically demanding borane (9-BBN) is generated by the double addition of borane to 1,5-cyclooctadiene:


The reactivity and selectivity of the borane reagent may be modified through the use of borane-Lewis base complexes.

Recent Literature

Hydroboration. 97. Synthesis of New Exceptional Chloroborane-Lewis Base Adducts for Hydroboration. Dioxane-Monochloroborane as a Superior Reagent for the Selective Hydroboration of Terminal Alkenes
J. V. B. Kanth, H. C. Brown, J. Org. Chem, 2001, 66, 5359-5365.

Hydroboration with Pyridine Borane at Room Temperature
J. M. Clay, E. Vedejs, J. Am. Chem. Soc., 2005, 127, 5766-5767.

Hydroboration with Pyridine Borane at Room Temperature
J. M. Clay, E. Vedejs, J. Am. Chem. Soc., 2005, 127, 5766-5767.

Sodium perborate: a mild and convenient reagent for efficiently oxidizing organoboranes
G. W. Kabalka, T. M. Shoup, N. M. Goudgaon, J. Org. Chem., 1989, 5930-5933.

Dod-S-Me and Methyl 6-Morpholinohexyl Sulfide (MMS) as New Odorless Borane Carriers
P. K. Patra, K. Nishide, K. Fuji, M. Node, Synthesis, 2004, 1003-1006.

Synthesis of Tertiary Alkyl Amines from Terminal Alkenes: Copper-Catalyzed Amination of Alkyl Boranes
R. P. Rucker, A. M. Whittaker, H. Dang, G. Lalic, J. Am. Chem. Soc., 2012, 134, 6571-6574.

A mild hydroboration of various 1-alkynes with pinacolborane was achieved in the presence of a catalytic amount of dicyclohexylborane at room temperature under neat conditions to afford the corresponding (E)-1-alkenylboronic acid pinacol esters in good yields.
K. Shirakawa, A. Arase, M. Hoshi, Synthesis, 2004, 1814-1820.

Highly Stereoselective Synthesis of cis-Alkenyl Pinacolboronates and Potassium cis-Alkenyltrifluoroborates via a Hydroboration/Protodeboronation Approach
G. A. Molander, N. M. Ellis, J. Org. Chem., 2008, 73, 6841-6844.

Iron-Catalyzed 1,4-Hydroboration of 1,3-Dienes
J. Y. Wu, B. Moreau, T. Ritter, J. Am. Chem. Soc., 2009, 131, 12915-12917.

Nickel-Catalyzed 1,4-Addition of Trialkylboranes to α,β-Unsaturated Esters: Dramatic Enhancement by Addition of Methanol
K. Hirano, H. Yorimitsu, K. Oshima, Org. Lett., 2007, 9, 1541-1544.

Regioselective Semihydrogenation of Dienes
T. J. A. Graham, T. H. Poole, C. N. Reese, B. C. Goess, J. Org. Chem., 2011, 76, 4132-4138.

Concise Formation of 4-Benzyl Piperidines and Related Derivatives Using a Suzuki Protocol
S. Vice, T. Bara, A. Bauer, C. A. Evans, J. Fort, H. Josien, S. McCombie, M. Miller, D. Nazzareno, A. Palani, J. Tagat,  J. Org. Chem, 2001, 66, 2487-2492.

An Exceptional Hydroboration of Substituted Fluoroolefins Providing Tertiary Alcohols
P. V. Ramachandran, M. P. Jennings, Org. Lett., 2001, 3, 3789-3790.