Thexylborane

Thexylborane
	; Dimeric form of thexylborane
Identifiers
CAS Number	monomer: 3688-24-2; dimer: 37099-64-2;
3D model (JSmol)	monomer: Interactive image; dimer: Interactive image;
ChemSpider	monomer: 4483657;
PubChem CID	monomer: 10877414;
	InChI Key: AAYWIXGLVAEPTP-UHFFFAOYSA-N; monomer: InChI=1S/C6H13B/c1-5(2)6(3,4)7/h5H,1-4H3;
	SMILES 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
Chemical formula	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). Infobox references

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.

[syn-1] 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.

[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.

[1]

[2]