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 (JSmol)	Interactive image;
ChemSpider	17206399 ;
ECHA InfoCard	100.157.575
PubChem CID	9921373 R; 10890567 S;
CompTox Dashboard (EPA)	DTXSID50432857 ;
	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
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H250
Precautionary statements	P210, P222, P280, P302+P334, P370+P378, P422
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Alpine borane is the commercial name for an organoboron compound that is used in organic synthesis. It is a colorless liquid, although it is usually encountered as a solution.

Preparation and reactions

This reagent is generated by treating 9-BBN with α-pinene.[2]

This sterically crowded chiral trialkylborane can stereoselectively reduce aldehydes in what is known as the Midland Alpine borane reduction, or simply the Midland reduction.[3]

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.[4]

The reaction is proposed to involve formation of an adduct by coordination of the carbonyl oxygen to boron. Intramolecular hydride transfer from the pinane substituent to the carbonyl carbon ensues.[2]

Related reagents

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

References

R-Alpine-Borane and S-Alpine-Borane at Sigma-Aldrich
M. M. Midland (1989). "Asymmetric reductions with organoborane reagents". Chemical Reviews. 89 (7): 1553–1561. doi:10.1021/cr00097a010.
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
Midland, M. Mark; Graham, Richard S. (1985). "Asymmetric Reduction of α,β-Acetylenic Ketones with B-3-Pinanyl-9-Borabicyclo[3.3.1]nonane: (R)-(+)-1-Octyln-3-ol". 63: 57. doi:10.15227/orgsyn.063.0057. {{cite journal}}: Cite journal requires |journal= (help)

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[1] R-Alpine-Borane and S-Alpine-Borane at Sigma-Aldrich

[CR-2] M. M. Midland (1989). "Asymmetric reductions with organoborane reagents". Chemical Reviews. 89 (7): 1553–1561. doi:10.1021/cr00097a010.

[3] 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

[4] Midland, M. Mark; Graham, Richard S. (1985). "Asymmetric Reduction of α,β-Acetylenic Ketones with B-3-Pinanyl-9-Borabicyclo[3.3.1]nonane: (R)-(+)-1-Octyln-3-ol". 63: 57. doi:10.15227/orgsyn.063.0057. {{cite journal}}: Cite journal requires |journal= (help)