View source for 1,1′-Bi-2-naphthol

{{chembox
| verifiedrevid = 413087241
| Name = 1,1{{prime}}-Bi-2-naphthol
| ImageFile = 
| ImageFileL1 = R-BINOL-2D-skeletal.png
| ImageNameL1 = Skeletal formula of R-BINOL
| ImageFileR1 = S-BINOL-2D-skeletal.png
| ImageNameR1 = Skeletal formula of S-BINOL
| ImageFileL2 = R-BINOL-3D-balls.png
| ImageNameL2 = Ball-and-stick model of R-BINOL
| ImageFileR2 = S-BINOL-3D-balls.png
| ImageNameR2 = Ball-and-stick model of S-BINOL
| ImageCaptionL2 = (''R'')-(+)-BINOL 
| ImageCaptionR2 = (''S'')-(−)-BINOL
| PIN = [1,1{{prime}}-Binaphthalene]-2,2{{prime}}-diol
| OtherNames = {{Unbulleted list
  | 1,1{{prime}}-Bi-2-naphthol
  | 1,1-Binaphthol
  | BINOL
  | Binol
  }}
| SystematicName = 
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 11269
| PubChem = 11762
| InChI = 1/C20H14O2/c21-17-11-9-13-5-1-3-7-15(13)19(17)20-16-8-4-2-6-14(16)10-12-18(20)22/h1-12,21-22H
| InChIKey = PPTXVXKCQZKFBN-UHFFFAOYAX
| SMILES = C1=CC=C2C(=C1)C=CC(=C2C3=C(C=CC4=CC=CC=C43)O)O
| SMILES_Comment = (''R''/''S'')
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 138718
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C20H14O2/c21-17-11-9-13-5-1-3-7-15(13)19(17)20-16-8-4-2-6-14(16)10-12-18(20)22/h1-12,21-22H
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = PPTXVXKCQZKFBN-UHFFFAOYSA-N
| CASNo = 602-09-5
| CASNo_Comment = (''R''/''S'')
| CASNo1 = 18531-94-7
| CASNo1_Comment = (''R'')-(+)
| CASNo2 = 18531-99-2
| CASNo2_Comment = (''S'')-(−)
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 25AB254328
| UNII_Comment = (''R''/''S'')
| UNII1_Ref = {{fdacite|correct|FDA}}
| UNII1 = M6IDZ128WT
| UNII1_Comment = (''R'')-(+)
| UNII2_Ref = {{fdacite|correct|FDA}}
| UNII2 = 54OT5RRV4C
| UNII2_Comment = (''S'')-(−)
}}
| Section2 = {{Chembox Properties
| Formula =
| C=20 | H=14 | O=2   
| MolarMass = 286.32 g/mol  
| Density = 
| MeltingPtC = 205 to 211
| MeltingPt_ref = <ref>[http://www.chemexper.com/chemicals/supplier/cas/18531-94-7.html Datasheet], chemexper.com</ref>
  }}
| Section3 = 
| Section4 = 
| Section5 = 
| Section6 = 
}}

'''1,1{{prime}}-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 [[enantiomer]]s can be readily separated and are stable toward [[racemisation]].  The [[specific rotation]] of the two [[enantiomers]] is 35.5° (''c'' = 1 in [[THF]]), with the ''R'' enantiomer being the [[dextrorotary]] one. BINOL is a precursor for another [[chiral ligand]] called [[BINAP]]. The volumetric mass [[density]] of the two enantiomers is 0.62 g&nbsp;cm{{sup|−3}}.{{citation needed|date=January 2022}}

==Preparation==
The [[organic synthesis]] of BINOL is not a challenge as such but the preparation of the individual [[enantiomer]]s 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 (''S'')-(+)-[[amphetamine]].<ref>{{cite journal|last1 = Brussee|first1 = J.|last2 = Jansen|first2 = A. C. A.|year = 1983|title = A highly stereoselective synthesis of ''S''-(−)-[1,1{{prime}}-binaphthalene]-2,2{{prime}}-diol|journal = Tetrahedron Letters|volume = 24|issue = 31|pages = 3261–3262|doi = 10.1016/S0040-4039(00)88151-4}}</ref>

[[File:CuCl2 naphthol coupling.png|400px]]

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) reducing into iron(II).

[[Optically active]] BINOL can also be obtained from [[racemic]] BINOL by optical resolution. In one method, the [[alkaloid]] N-benzylcinchonidinium chloride forms a crystalline [[inclusion compound]]. The inclusion compound of the (''S'')-enantiomer is soluble in [[acetonitrile]] but that of the (''R'')-enantiomer is not.<ref name="orgsyn">[http://www.orgsyn.org/orgsyn/prep.asp?prep=v76p0001 "RESOLUTION OF  1,1'-BI-2-NAPHTHOL"] {{Webarchive|url=https://web.archive.org/web/20120716191712/http://www.orgsyn.org/orgsyn/prep.asp?prep=v76p0001 |date=2012-07-16 }}, Dongwei Cai, David L. Hughes, Thomas R. Verhoeven, and Paul J. Reider, in [[Organic Syntheses]] Coll. Vol. 10, p.93; Vol. 76, p.1</ref> In another method BINOL is esterified with [[pentanoyl chloride]]. The enzyme [[cholesterol]] [[esterase]] [[Hydrolysis|hydrolyse]]s the (''S'')-diester but not the (''R'')-diester.<ref name="orgsyn" /> The (''R'')-dipentanoate is hydrolysed in a second step with [[sodium methoxide]].<ref name="orgsyn2">[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv9p0077 "(''S'')-(−)- and (''R'')-(+)-1,1{{prime}}-bi-2-naphthol"] {{Webarchive|url=https://web.archive.org/web/20050418112746/http://www.orgsyn.org/orgsyn/prep.asp?prep=CV9P0077 |date=2005-04-18 }}, Romas J. Kazlauskas in [[Organic Syntheses]], Coll. Vol. 9, p.77; Vol. 70, p.60</ref> The third method employs [[High-performance liquid chromatography|HPLC]] with chiral stationary phases.<ref>{{cite journal|last1 = Landek|first1 = G.|last2 = Vinković|first2 = M.|last3 = Kontrec|first3 = D.|last4 = Vinković|first4 = V.|year = 2006| title = Influence of mobile phase and temperature on separation of 1,1{{prime}}-binaphthyl-2,2{{prime}}-diol enantiomers with brush type chiral stationary phases derived from L-leucine|journal = Chromatographia|volume = 64|issue = 7–8|pages = 469–473|doi = 10.1365/s10337-006-0041-5| s2cid=95785346 }}</ref>

==BINOL derivatives==
[[File:Chiral phosphoric acid.png|thumb|left|162px|Structure of a [[chiral phosphoric acid]] derived from BINOL.<ref>{{cite journal |doi=10.1021/cr5001496|title=Complete Field Guide to Asymmetric BINOL-Phosphate Derived Brønsted Acid and Metal Catalysis: History and Classification by Mode of Activation; Brønsted Acidity, Hydrogen Bonding, Ion Pairing, and Metal Phosphates|year=2014|last1=Parmar|first1=Dixit|last2=Sugiono|first2=Erli|last3=Raja|first3=Sadiya|last4=Rueping|first4=Magnus|journal=Chemical Reviews|volume=114|issue=18|pages=9047–9153|pmid=25203602|doi-access=free}}</ref>]]
Aside from the starting materials derived directly from the [[Chiral pool synthesis|chiral pool]], (''R'')- and (''S'')-BINOL in high enantiopurity (>99% [[enantiomeric excess]]) are two of the most inexpensive sources of chirality for organic synthesis, costing less than US$0.60 per gram when purchased in bulk from chemical suppliers.<ref>{{Cite journal|last1=Yang|first1=Jin-Fei|last2=Wang|first2=Rong-Hua|last3=Wang|first3=Yin-Xia|last4=Yao|first4=Wei-Wei|last5=Liu|first5=Qi-Sheng|last6=Ye|first6=Mengchun|date=2016-10-11|title=Ligand-Accelerated Direct C−H Arylation of BINOL: A Rapid One-Step Synthesis of Racemic 3,3{{prime}}-Diaryl BINOLs|journal=Angewandte Chemie International Edition|language=en|volume=55|issue=45|pages=14116–14120|doi=10.1002/anie.201607893|pmid=27726256 |issn=1433-7851}}</ref>  As a consequence, it serves as an important starting material for other sources of chirality for stereoselective synthesis, both stoichiometric and substoichiometric (catalytic).

Many important chiral ligands are constructed from the binaphthyl scaffold and ultimately derived from BINOL as a starting material, [[BINAP]] being one of the most well known and important.

The compound aluminium lithium bis(binaphthoxide) (ALB) is prepared by reaction of BINOL with [[lithium aluminium hydride]].<ref>''A practical large-scale synthesis of enantiomerically pure 3-[bis(methoxycarbonyl)methyl]cyclohexanone via catalytic asymmetric Michael reaction'' [[Tetrahedron (journal)|Tetrahedron]], Volume 58, Issue 13, 25 March '''2002''', Pages 2585–2588 Youjun Xu, Ken Ohori, Takashi Ohshima, Masakatsu Shibasaki {{doi|10.1016/S0040-4020(02)00141-2}}</ref>  In a different stoichiometric ratio (1:1 BINOL/LiAlH<sub>4</sub> instead of 2:1), the chiral reducing agent BINAL (lithium dihydrido(binaphthoxy)aluminate) is produced.<ref>{{Citation|last1=Gopalan|first1=Aravamudan S.|title=Lithium Aluminum Hydride-2,2{{prime}}-Dihydroxy-1,1{{prime}}-binaphthyl|date=2001-04-15|encyclopedia=Encyclopedia of Reagents for Organic Synthesis|publisher=John Wiley & Sons, Ltd|language=en|doi=10.1002/047084289x.rl041|isbn=0471936235|last2=Jacobs|first2=Hollie K.}}</ref>

:[[File:AlLibis(binaphthoxide).svg|450px]]

It has been employed in an [[asymmetric Michael reaction]] with [[cyclohexenone]] and [[dimethyl malonate]]:

:[[File:AsymmetricMichael Shibasaki 2002.svg|343px]]

==See also==
* [[Shibasaki catalysts]]

==References==
{{Reflist}}

{{DEFAULTSORT:Bi-2-Naphthol, 1, 1'-}}
[[Category:2-Naphthols]]
[[Category:Dimers (chemistry)]]
[[Category:Diols]]