1,1'-Bi-2-naphthol

Chembox new
Name = 1,1-Bi-2-naphthol
ImageFileL1 = R-BINOL-2D-skeletal.png ImageSizeL1 = 100px
ImageNameL1 = R-BINOL
ImageFileR1 = S-BINOL-2D-skeletal.png ImageSizeR1 = 100px
ImageNameR1 = S-BINOL
ImageFile2 = BINOL 3D.png ImageSize2 = 150px
IUPACName = 1,1'-Binaphthalene-2,2'-diol
OtherNames = 1,1'-Bi-2-naphthol
1,1-Binaphthol
BINOL
Section1 = Chembox Identifiers
CASNos = Racemic: [602-09-5]
(R)-(+): [18531-94-7]
(S)-(-): [18531-99-2]
SMILES =Oc1c(c2c(O)ccc3c2cccc3)c(cccc4)c4cc1
Section2 = Chembox Properties
Formula = C₂₀H₁₄O₂
MolarMass = 286.32 g/mol
Density =
MeltingPt = 205-211 °C

1,1'-Bi-2-naphthol (BINOL) is an organic compound that is often used as a ligand for transition-metal catalysed asymmetric synthesis. BINOL has axial chirality and the two enantiomers can be readily separated and are stable toward racemisation. The specific rotation of the two enatiomers is +/- 35.5° (c=1 in THF). BINOL is a precursor for another chiral ligand called BINAP. [http://www.rhodia-phosphines.com/docs/Rhodia.pdf "Bin
] ]

Preparation

The organic synthesis of BINOL is not a challenge as such but the preparation of the individual enantiomers is.

("S")-BINOL can be prepared directly from an asymmetric oxidative coupling of 2-naphthol with copper(II) chloride. The chiral ligand in this reaction is (+)-amphetamine.

Racemic BINOL can also be produced using iron(III) chloride as an oxidant. The mechanism involves complexation of iron(III) into the hydroxyl, followed by a radical coupling reaction of the naphthol rings initiated by iron(III) oxidizing into iron(II).

Optically active BINOL can also be obtained from racemic BINOL by optical resolution. In one method, the alkaloid N-benzylcinchonidinium chloride form a crystalline inclusion compound. The inclusion compound of the "S"-enantiomer is soluble in acetonitrile but that of the "R"-enantiomer is not. [http://www.orgsyn.org/orgsyn/prep.asp?prep=v76p0001 "RESOLUTION OF 1,1'-BI-2-NAPHTHOL"] , Dongwei Cai, David L. Hughes, Thomas R. Verhoeven, and Paul J. Reider, in Organic Syntheses Coll. Vol. 10, p.93; Vol. 76, p.1]

In another method BINOL is reacted with the acid chloride pentanoyl chloride to obtain the di-ester compound. The enzyme cholesterol esterase is then added in the form of bovine pancreas acetone powder which is able to hydrolyse the ("S")-di-ester but not the ("R")-di-ester. The ("R")-dipentanoate is hydrolysed in a second step with sodium methoxide. [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv9p0077 "(S)-(−)- AND (R)-(+)-1,1'-BI-2-NAPHTHOL"] , Romas J. Kazlauskas in Organic Syntheses, Coll. Vol. 9, p.77; Vol. 70, p.60]

Third method employs HPLC with chiral stationary phases. A very efficient phase is described here [cite journal
last = Landek
first = G.
coauthors = Vinković M., Kontrec D. and Vinković V.
year = 2006
date=2006
title = Influence of mobile phase and temperature on separation of 1,1 '-binaphthyl-2,2 '-diol enantiomers with brush type chiral stationary phases derived from L-leucine
journal = Chromatographia
volume = 64
pages = 469–473
doi = 10.1365/s10337-006-0041-5] .

References

External links

* [http://www.chemexper.com/chemicals/supplier/cas/18531-94-7.html Datasheet]