Disiamylborane (bis(1,2-dimethylpropyl)borane) is an organoborane with the formula [((CH3)2CHCH(CH3))2BH]2 (abbreviation: Sia2BH). It is a colorless waxy solid that is used in organic synthesis for hydroboration–oxidation reactions. Like most dialkyl boron hydrides, it has a dimeric structure with bridging hydrides.

Disiamylborane
Skeletal formula of disiamylborane
Names
IUPAC name
Bis(1,2-dimethylpropyl)borane
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/C10H23B/c1-7(2)9(5)11-10(6)8(3)4/h7-11H,1-6H3 checkY
    Key: HXJFQNUWPUICNY-UHFFFAOYSA-N checkY
  • InChI=1/C10H23B/c1-7(2)9(5)11-10(6)8(3)4/h7-11H,1-6H3
    Key: HXJFQNUWPUICNY-UHFFFAOYAY
  • CC(C(C)C)BC(C)C(C)C
  • B(C(C(C)C)C)C(C)C(C)C
Properties
C10H23B
Molar mass 154.09 g/mol
Melting point 35-40 °C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Reactions

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Disiamylborane is prepared by hydroboration of trimethylethylene with diborane.[1] The reaction stops at the secondary borane due to steric hindrance.

Disiamylborane is relatively selective for terminal alkynes and alkenes vs internal alkynes and alkenes. Like most hydroboration, the addition proceeds in an anti-Markovnikov manner.[1] It can be used to convert terminal alkynes, into aldehydes.

The hydroboration process proceeds via an initial dissociation of the dimer.[2]

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Naming

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The prefix disiamyl is an abbreviation for "di-sec-isoamyl", where sec-isoamyl ("secondary isoamyl") is an archaic name for the 1,2-dimethylpropyl group (amyl being a obsolescent synonym of pentyl).

References

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  1. ^ a b Eric J. Leopold (1986). "Selective Hydroboration of a 1,3,7-Triene: Homogeraniol". Organic Syntheses. 64: 164. doi:10.15227/orgsyn.064.0164.
  2. ^ Chandrasekharan, J.; Brown, Herbert C. (1985). "Hydroboration kinetics. 11. A reinvestigation of the kinetics of hydroboration of representative alkenes with disiamylborane dimer. Conclusive evidence for the dissociation mechanism in the hydroboration of alkenes with dialkylborane dimers". The Journal of Organic Chemistry. 50 (4): 518–520. doi:10.1021/jo00204a019.