Alpine borane

Alpine borane^[1]

Names
IUPAC name 9-(2,6,6-Trimethylbicyclo[3.1.1]hept-3-yl)-9-bora-bicyclo[3.3.1]nonane
Other names Alpine-Borane; B-Isopinocampheyl-9-borabicyclo[3.3.1]nonane; B-3-Pinanyl-9-borabicyclo[3.3.1]nonane
Identifiers
CAS Number	73624-47-2 (R isomer) 42371-63-1 (S isomer)
3D model (Jmol)	Interactive image
ChemSpider	17206399
ECHA InfoCard	100.157.575
InChI InChI=1S/C18H31B/c1-12-16-10-13(18(16,2)3)11-17(12)19-14-6-4-7-15(19)9-5-8-14/h12-17H,4-11H2,1-3H3/t12-,13-,14?,15?,16+,17-/m1/s1 Key: VCDGSBJCRYTLNU-AZWGFFAPSA-N InChI=1/C18H31B/c1-12-16-10-13(18(16,2)3)11-17(12)19-14-6-4-7-15(19)9-5-8-14/h12-17H,4-11H2,1-3H3/t12-,13-,14?,15?,16+,17-/m1/s1 Key: VCDGSBJCRYTLNU-AZWGFFAPBY
SMILES CC4(C)[C@@H]1C[C@H]4[C@@H](C)[C@@H](C1)B3C2CCCC3CCC2
Properties
Chemical formula	C18H31B
Molar mass	258.26 g·mol^−1
Appearance	Colorless liquid
Density	0.947 g/mL
Boiling point	> 55 °C (131 °F; 328 K)
Hazards
EU classification (DSD)	F
R-phrases	R17
S-phrases	S6 S16 S24 S36/37/39
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Alpine borane is the commercial name for an organoboron compound that is used in organic synthesis. This reagent is generated by treating 9-BBN with α-pinene to give a sterically crowded trialkylborane. The resulting chiral species can stereoselectively reduce ketones, aldehydes, even deutero aldehydes in what is known as the Midland Alpine Borane Reduction, or simply the Midland Reduction:^[2]

C₈H₁₂B-pinanyl + RCDO → C₈H₁₂BOCHDR + (+)-d-pinene

Hydrolysis of the resulting borinic ester affords the alcohol:

C₈H₁₂BOCHDR + H₂O → C₈H₁₂BOH + HOCHDR

It is also effective for the stereoselective reduction of certain acetylenic ketones.^[3]

Related reagents

A range of alkyl-substituted derivatives of borane and diborane are specialty reagents in organic synthesis. Two such reagents that are closely related to Alpine borane are 9-BBN and diisopinocampheylborane.

References

1. R-Alpine-Borane and S-Alpine-Borane at Sigma-Aldrich
2. M. Mark Midland "B-3-Pinanyl-9-borabicyclo[3.3.1]nonane" in Encyclopedia of Reagents for Organic Synthesis 2001 John Wiley, New York.doi:10.1002/047084289X.rp173. Article Online Posting Date: April 15, 2001
3. M. Mark Midland and Richard S. Graham. "Asymmetric Reduction of α,β-Acetylenic Ketones with B-3-Pinanyl-9-Borabicyclo[3.3.1]nonane: (R)-(+)-1-Octyln-3-ol". Org. Synth.; Coll. Vol., 7, p. 402