Master Organic Chemistry Reaction Guide

Hydroboration of alkynes using BH3 to give aldehydes

Description: When alkynes are treated with BH3 and subsequently treated with H2O2, they are converted into aldehydes.
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Further Reading

  1. THE HYDROBORATION OF ACETYLENES – A CONVENIENT CONVERSION OF INTERNAL ACETYLENES TO CIS OLEFINS OF HIGH PURITY AND OF TERMINAL ACETYLENES TO ALDEHYDES
    Brown, H.C.; Zweifel, G. Am. Chem. Soc. 1959 81 (6), 1512 DOI: 10.1021/ja01515a058
    The original paper describing the hydroboration of alkynes, by Nobel Laureate Prof. H. C. Brown (Purdue).
  2. PALLADIUM-CATALYZED REACTION OF 1-ALKENYLBORONATES WITH VINYLIC HALIDES: (1Z,3E)-1-PHENYL-1,3-OCTADIENE
    Miayura, N.; Suzuki, A. Org. Synth. 1990, 68, 130 DOI:15227/orgsyn.068.0130
    A procedure by Nobel Laureate Akira Suzuki for the hydroboration of an alkyne with catecholborane. The resulting product can then be subsequently used in a Pd-catalyzed Suzuki coupling reaction.
    A variety of other reagents were developed by H. C. Brown for hydroboration, including catecholborane, 9-BBN, and disiamylborane. The advantage with these reagents is that they will undergo monoadditionto alkynes, whereas borane will add twice. Representative references for the reaction of these reagents with alkynes are below:
  3. Catecholborane (1,3,2-Benzodioxaborole) as a New, General Monohydroboration Reagent for Alkynes. A Convenient Synthesis of Alkeneboronic Esters and Acids from Alkynes via Hydroboration
    Brown, H. C.; Gupta, S. K. Am. Chem. Soc. 1972 94 (12), 4370 DOI: 10.1021/ja00767a072
  4. 50. Hydroboration of Representative Alkynes with 9-Borabicyclo[3.3.1]nonane-a Simple Synthesis of Versatile Vinyl Bora and gem-Dibora Intermediates
    Brown, H. C.; Scouten, C. G.; Liotta, R. J. Am. Chem. Soc. 1979 101 (1), 96 DOI:10.1021/ja00495a016
  5. XI. The Hydroboration of Acetylenes-A Convenient Conversion of Internal Acetylenes into cis-Olefins and of Terminal Acetylenes into Aldehydes
    Brown, H. C.; Zweifel, G. J. Am. Chem. Soc. 1961, 83(18), 3834 DOI: 10.1021/ja01479a024
    This paper describes the use of disiamylborane for the selective monohydroboration of alkynes.

 

Comments

Comment section

5 thoughts on “Hydroboration of alkynes using BH3 to give aldehydes

  1. This is SOO helpful! Thank you. I’m only in OChem 1 and often they tell us not to worry about knowing these longer mechanisms, but just seeing them and having them explained once or twice helps me understand everything else!
    Thanks again for breaking it down into bite-sized pieces!

  2. ” Then comes the weird step! The carbon-boron bond breaks, and the examples from this bond migrate to the oxygen”
    Do you mean to say examples here or do you mean something else (electrons?)

  3. Can example 3 also form two products equally like example 4 because the double bond being on the adjacent carbon would still result it being on a carbon that is equally substituted correct? I am having a hard time seeing the difference between example 4 and 3 both look like the two options are both on secondary carbons

    1. In example 3, no matter what side of the alkyne is added to, the product is still 2-butanone. remember that there is no such thing as 3-butanone since we always number the molecule in such a way as to keep the number the lowest.

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