Thexylborane

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Thexylborane
Thexylborane.svg
Dimeric form of thexylborane
Identifiers
3D model (JSmol)
ChemSpider
  • Key: AAYWIXGLVAEPTP-UHFFFAOYSA-N
  • monomer: InChI=1S/C6H13B/c1-5(2)6(3,4)7/h5H,1-4H3
  • monomer: [B]C(C)(C)C(C)C
  • dimer: [H]1[BH]([H][BH]1C(C)(C)C(C)C)C(C)(C)C(C)C
Properties
C12H30B2
Molar mass 195.99 g·mol−1
Appearance colorless liquid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Thexylborane is a borane with the formula [Me2CHCMe2BH2]2 (Me = methyl). The name derives from "t-hexylborane" (although the group is not the standard tert-hexyl group), and the formula is often abbreviated ThxBH2. A colorless liquid, it is a rare, easily accessed monoalkylborane. It is produced by the hydroboration of tetramethylethylene:[1]

B2H6 + 2 Me2C=CMe2 → [Me2CHCMe2BH2]2

Reactions[edit]

Thexylborane is generated in situ. In solution, it isomerizes over the course several days to the 2,3-dimethyl-1-butyl derivative, shown as the monomer here:

Me2CHCMe2BH2 → Me2CHCH(Me)CH2BH2

Thexylborane allows the synthesis of ketones by coupling a pair of alkenes with carbon monoxide, which serves as a carbonyl linchpin:[1]

Me2CHCMe2BH2 + 2 RCH=CH2 → Me2CHCH(Me)CH2B(CH2CH2R)2
Me2CHCH(Me)CH2B(CH2CH2R)2 + CO + H2O → O=C(CH2CH2R)2 + ...

An important feature of this reagent is that the thexyl group almost never undergoes anionotropic 1,2-migration from boron to a neighboring atom.[2]

References[edit]

  1. ^ a b Negishi, Ei-Ichi; Brown, Herbert C. (1974). "Thexylborane-A Highly Versatile Reagent for Organic Synthesis via Hydroboration". Synthesis. 1974 (2): 77–89. doi:10.1055/s-1974-23248.
  2. ^ Aggarwal, Varinder K.; Fang, Guang Yu; Ginesta, Xavier; Howells, Dean M.; Zaja, Mirko (2006-01-01). "Toward an understanding of the factors responsible for the 1,2-migration of alkyl groups in borate complexes". Pure and Applied Chemistry. 78 (2): 215–229. doi:10.1351/pac200678020215. ISSN 1365-3075. S2CID 13833993.