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 monoalkylborane. It is produced by the hydroboration of tetramethylethylene:[1]
- B2H6 + 2 Me2C=CMe2 → [Me2CHCMe2BH2]2
Reactions
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
- ^ 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. S2CID 96012955.
- ^ 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.
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