1,1-Bi-2-naphthol (BINOL) is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

that is often used as a

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

for transition-metal catalysed

asymmetric synthesis Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecul ...

. BINOL has

axial chirality In chemistry, axial chirality is a special case of chirality (chemistry), chirality in which a molecule contains two pairs of chemical groups in a non-planar arrangement about an axis of chirality so that the molecule is not superposable on its mi ...

and the two

enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

s can be readily separated and are stable toward racemisation. The

specific rotation In chemistry, specific rotation ( �'') is a property of a chiral chemical compound. It is defined as the change in orientation of monochromatic plane-polarized light, per unit distance–concentration product, as the light passes through a sampl ...

of the two

enantiomers In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

is 35.5° (''c'' = 1 in

THF Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is ma ...

), with the ''R'' enantiomer being the

dextrorotary Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular ...

one. BINOL is a precursor for another

chiral ligand Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecul ...

called

BINAP BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is an organophosphorus compound. This Optical isomerism, chiral diphosphines, diphosphine ligand is widely used in chiral synthesis, asymmetric synthesis. It consists of a pair of 2-diphe ...

. The volumetric mass

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

of the two enantiomers is 0.62 g cm.

Preparation

The

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

of BINOL is not a challenge as such but the preparation of the individual

s is. (''S'')-BINOL can be prepared directly from an asymmetric

oxidative coupling Oxidative coupling in chemistry is a coupling reaction of two molecular entities through an oxidative process. Usually oxidative couplings are catalysed by a transition metal complex like in classical cross-coupling reactions, although the under ...

2-naphthol 2-Naphthol, or β-naphthol, is a fluorescent colorless (or occasionally yellow) crystalline solid with the formula C10H7OH. It is an isomer of 1-naphthol, differing by the location of the hydroxyl group on the naphthalene ring. The naphthols are ...

with

copper(II) chloride Copper(II) chloride, also known as cupric chloride, is an inorganic compound with the chemical formula . The monoclinic crystal system, monoclinic yellowish-brown anhydrous form slowly absorbs moisture to form the orthorhombic blue-green hydrate, ...

. The

in this reaction is (''S'')-(+)-

amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...

Racemic BINOL can also be produced using

iron(III) chloride Iron(III) chloride describes the inorganic compounds with the formula (H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated f ...

as an oxidant. The mechanism involves complexation of iron(III) into the

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

, followed by a radical coupling reaction of the naphthol rings initiated by iron(III) reducing into iron(II).

Optically active Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circul ...

BINOL can also be obtained from

racemic In chemistry, a racemic mixture or racemate () is a mixture that has equal amounts (50:50) of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as r ...

BINOL by optical resolution. In one method, the

alkaloid Alkaloids are a broad class of natural product, naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids. Alkaloids are produced by a large varie ...

N-benzylcinchonidinium chloride forms a crystalline

inclusion compound Inclusion or Include may refer to: Sociology * Social inclusion, action taken to support people of different backgrounds sharing life together. ** Inclusion (disability rights), promotion of people with disabilities sharing various aspects of li ...

. The inclusion compound of the (''S'')-enantiomer is soluble in

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

but that of the (''R'')-enantiomer is not."RESOLUTION OF 1,1'-BI-2-NAPHTHOL"
, Dongwei Cai, David L. Hughes, Thomas R. Verhoeven, and Paul J. Reider, in

Organic Syntheses ''Organic Syntheses'' is a peer-reviewed scientific journal that was established in 1921. It publishes detailed and checked procedures for the synthesis of organic compounds. A unique feature of the review process is that all of the data and expe ...

Coll. Vol. 10, p.93; Vol. 76, p.1 In another method BINOL is esterified with

pentanoyl chloride Pentanoyl chloride is an acyl chloride derived from pentanoic acid. It is a colorless liquid that is used to attach the valeroyl group. It is usually produced by chlorination of valeric acid. Reactions Like related acyl chlorides, valeryl chlori ...

. The enzyme

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

esterase In biochemistry, an esterase is a class of enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis (and as such, it is a type of hydrolase). A wide range of different esterases exist that differ ...

hydrolyse Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

s the (''S'')-diester but not the (''R'')-diester. The (''R'')-dipentanoate is hydrolysed in a second step with

sodium methoxide Sodium methoxide is the simplest sodium alkoxide. With the formula , it is a white solid, which is formed by the deprotonation of methanol. It is a widely used reagent in industry and the laboratory. It is also a dangerously caustic base. ...

."(''S'')-(−)- and (''R'')-(+)-1,1-bi-2-naphthol"
, Romas J. Kazlauskas in

, Coll. Vol. 9, p.77; Vol. 70, p.60 The third method employs

HPLC High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify specific components in mixtures. The mixtures can origina ...

with chiral stationary phases.

BINOL derivatives

Aside from the starting materials derived directly from the

chiral pool The chiral pool is a "collection of abundant enantiopure building blocks provided by nature" used in synthesis. In other words, a chiral pool would be a large quantity of common organic enantiomers. Contributors to the chiral pool are amino acids, s ...

, (''R'')- and (''S'')-BINOL in high enantiopurity (>99%

enantiomeric excess In stereochemistry, enantiomeric excess (ee) is a measurement of purity used for chiral substances. It reflects the degree to which a sample contains one enantiomer in greater amounts than the other. A racemic mixture has an ee of 0%, while a sing ...

) 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. 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,

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 Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula or . It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthe ...

. In a different stoichiometric ratio (1:1 BINOL/LiAlH₄ instead of 2:1), the chiral reducing agent BINAL (lithium dihydrido(binaphthoxy)aluminate) is produced. : It has been employed in an asymmetric Michael reaction with cyclohexenone and

dimethyl malonate Dimethyl malonate is a diester derivative of malonic acid. It is a common reagent for organic synthesis used, for example, as a precursor for barbituric acid. It is also used in the malonic ester synthesis. It can be synthesized from dimethoxymeth ...

: :

References

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

Preparation

BINOL derivatives

See also

References