Desymmetrization

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Desymmetrization is a chemical reaction that converts prochiral substrates into chiral products. Desymmetrisations are so pervasive that they are rarely described as such except when they proceed enantioselectively. The enantioselective reactions require chiral catalysts or chiral reagents. [1] According to IUPAC, desymmetrization involves the "... the conversion of a prochiral molecular entity into a chiral one." [2]

Contents

Examples

Typical substrates are epoxides, diols, dienes, and cyclic carboxylic acid anhydrides. [1]

One example is the conversion of cis-3,5-diacetoxycyclopentene to monoacetate. This particular conversion utilizes the enzyme cholinesterase. [3]

DesymDiacetate.png

In another example, a symmetrical cyclic imide is subjected to asymmetric deprotonation resulting in a chiral product with high enantioselectivity. [4]

Partial hydrogenation]] converts benzil (PhC(O)C(O)Ph) into chiral hydrobenzoin. The process can be implemented enantioselectively using transfer hydrogenation. [5]

PhC(O)C(O)Ph + H2 → PhCH(OH)C(O)Ph (Ph = C6H5)

The precursor benzil has C2v symmetry, and the product is C2 symmetric.

Citric acid is also a symmetric molecule that can be desymmetrized by partial methylation.

Desymmetrization of citric acid DesymmetrizeCitricAcid.svg
Desymmetrization of citric acid

The alcoholysis of cyclic anhydrides can be conducted enantiosymmetrically using chiral amine catalysts. [6]

A related example is the hydrolysis of prochiral diesters catalyzed by chiral phosphoric acids. [7]

Formal symmetry considerations

Desymmetrizations involve the loss of an improper axis of rotation (mirror plane, center of inversion, rotation-reflection axis). In other words, desymmetrisations convert prochiral precursors into chiral products. [8]

Related Research Articles

<span class="mw-page-title-main">Amide</span> Organic compounds of the form RC(=O)NR′R″

In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula R−C(=O)−NR′R″, where R, R', and R″ represent any group, typically organyl groups or hydrogen atoms. The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, as in asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid with the hydroxyl group replaced by an amine group ; or, equivalently, an acyl (alkanoyl) group joined to an amine group.

<span class="mw-page-title-main">Ketone</span> Organic compounds of the form >C=O

In organic chemistry, a ketone is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)−. The simplest ketone is acetone, with the formula (CH3)2CO. Many ketones are of great importance in biology and industry. Examples include many sugars (ketoses), many steroids, and the solvent acetone.

<span class="mw-page-title-main">Epoxide</span> Organic compounds with a carbon-carbon-oxygen ring

In organic chemistry, an epoxide is a cyclic ether, where the ether forms a three-atom ring: two atoms of carbon and one atom of oxygen. This triangular structure has substantial ring strain, making epoxides highly reactive, more so than other ethers. They are produced on a large scale for many applications. In general, low molecular weight epoxides are colourless and nonpolar, and often volatile.

<span class="mw-page-title-main">Imine</span> Organic compound or functional group containing a C=N bond

In organic chemistry, an imine is a functional group or organic compound containing a carbon–nitrogen double bond. The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions.

In organic chemistry, an acyl chloride is an organic compound with the functional group −C(=O)Cl. Their formula is usually written R−COCl, where R is a side chain. They are reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride, CH3COCl. Acyl chlorides are the most important subset of acyl halides.

<span class="mw-page-title-main">Acyl halide</span> Oxoacid compound with an –OH group replaced by a halogen

In organic chemistry, an acyl halide is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group.

<span class="mw-page-title-main">Imide</span> Class of chemical compounds

In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications, imides are best known as components of high-strength polymers, called polyimides. Inorganic imides are also known as solid state or gaseous compounds, and the imido group (=NH) can also act as a ligand.

<span class="mw-page-title-main">Organic acid anhydride</span> Any chemical compound having two acyl groups bonded to the same oxygen atom

An organic acid anhydride is an acid anhydride that is also an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. Thus, (CH3CO)2O is called acetic anhydride.Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride").

<span class="mw-page-title-main">Phosphorus tribromide</span> Chemical compound

Phosphorus tribromide is a colourless liquid with the formula PBr3. The liquid fumes in moist air due to hydrolysis and has a penetrating odour. It is used in the laboratory for the conversion of alcohols to alkyl bromides.

<span class="mw-page-title-main">Carbodiimide</span> Class of organic compounds with general structure RN=C=NR

In organic chemistry, a carbodiimide is a functional group with the formula RN=C=NR. On Earth they are exclusively synthetic, but in interstellar space the parent compound HN=C=NH has been detected by its maser emissions.

<span class="mw-page-title-main">Sulfoxide</span> Organic compound containing a sulfinyl group (>SO)

In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl functional group attached to two carbon atoms. It is a polar functional group. Sulfoxides are oxidized derivatives of sulfides. Examples of important sulfoxides are alliin, a precursor to the compound that gives freshly crushed garlic its aroma, and dimethyl sulfoxide (DMSO), a common solvent.

<span class="mw-page-title-main">Aza-Diels–Alder reaction</span>

The Aza-Diels–Alder reaction is a modification of the Diels–Alder reaction wherein a nitrogen replaces sp2 carbon. The nitrogen atom can be part of the diene or the dienophile.

The Strecker amino acid synthesis, also known simply as the Strecker synthesis, is a method for the synthesis of amino acids by the reaction of an aldehyde with cyanide in the presence of ammonia. The condensation reaction yields an α-aminonitrile, which is subsequently hydrolyzed to give the desired amino acid. The method is used for the commercial production of racemic methionine from methional.

Tetrahydropyran (THP) is the organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom. It is named by reference to pyran, which contains two double bonds, and may be produced from it by adding four hydrogens. In 2013, its preferred IUPAC name was established as oxane. The compound is a colourless volatile liquid. Derivatives of tetrahydropyran are, however, more common. 2-Tetrahydropyranyl (THP-) ethers derived from the reaction of alcohols and 3,4-dihydropyran are commonly used as protecting groups in organic synthesis. Furthermore, a tetrahydropyran ring system, i.e., five carbon atoms and an oxygen, is the core of pyranose sugars, such as glucose.

<span class="mw-page-title-main">Lead(IV) acetate</span> Organometallic compound (Pb(C2H3O2)4)

Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula Pb(C2H3O2)4. It is a colorless solid that is soluble in nonpolar, organic solvents, indicating that it is not a salt. It is degraded by moisture and is typically stored with additional acetic acid. The compound is used in organic synthesis.

<span class="mw-page-title-main">Titanium isopropoxide</span> Chemical compound

Titanium isopropoxide, also commonly referred to as titanium tetraisopropoxide or TTIP, is a chemical compound with the formula Ti{OCH(CH3)2}4. This alkoxide of titanium(IV) is used in organic synthesis and materials science. It is a diamagnetic tetrahedral molecule. Titanium isopropoxide is a component of the Sharpless epoxidation, a method for the synthesis of chiral epoxides.

<span class="mw-page-title-main">Diphenylethylenediamine</span> Chemical compound

1,2-Diphenyl-1,2-ethylenediamine, DPEN, is an organic compound with the formula H2NCHPhCHPhNH2, where Ph is phenyl (C6H5). DPEN exists as three stereoisomers: meso and two enantiomers S,S- and R,R-. The chiral diastereomers are used in asymmetric hydrogenation. Both diastereomers are bidentate ligands.

Asymmetric ester hydrolysis with pig liver esterase is the enantioselective conversion of an ester to a carboxylic acid through the action of the enzyme pig liver esterase. Asymmetric ester hydrolysis involves the selective reaction of one of a pair of either enantiotopic or enantiomorphic ester groups.

<span class="mw-page-title-main">Chiral phosphoric acid</span> Esters of phosphoric acid with a chiral backbone

In organic chemistry, chiral phosphoric acids are esters of phosphoric acid H3PO4 that have chiral backbones. Well known examples include cyclic diesters derived from the BINOL and TADDOL motifs. These compounds are used in asymmetric catalysis as chiral Brønsted acids and/or hydrogen-bond donors. The conjugate bases are also used in generating chiral ion pairs.

α,β-Unsaturated carbonyl compound Functional group of organic compounds

α,β-Unsaturated carbonyl compounds are organic compounds with the general structure (O=CR)−Cα=Cβ-R. Such compounds include enones and enals, but also carboxylic acids and the corresponding esters and amides. In these compounds, the carbonyl group is conjugated with an alkene. Unlike the case for carbonyls without a flanking alkene group, α,β-unsaturated carbonyl compounds are susceptible to attack by nucleophiles at the β-carbon. This pattern of reactivity is called vinylogous. Examples of unsaturated carbonyls are acrolein (propenal), mesityl oxide, acrylic acid, and maleic acid. Unsaturated carbonyls can be prepared in the laboratory in an aldol reaction and in the Perkin reaction.

References

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  2. "desymmetrization". IUPAC Gold Book. 2014. doi: 10.1351/goldbook.D01623 .
  3. Donald R. Deardorff, Colin Q. Windham, and Chris L. Craney "Enantioselective Hydrolysis of cis-3,5-diacetoxycyclopentene: (1R,4S)-(+)-4-Hydroxy-2-cyclopentenyl Acetate" Organic Syntheses, Coll. Vol. 9, p.487 (1998); Vol. 73, p.25 (1996).
  4. Vincent Rodeschini, Nigel S. Simpkins, and Fengzhi Zhang "Chiral lithium amide base desymmetrization of a ring fused imide: formation of (3as,7as)-2-[2-(3,4-dimethoxyphenyl)-ethyl]-1,3-dioxo-octahydro-isoindole-3a-carboxylic acid methyl ester" Org. Synth. 2007, volume 84, 306. doi : 10.15227/orgsyn.084.0306
  5. Takao Ikariya, Shohei Hashiguchi, Kunihiko Murata, and Ryōji Noyori (2005). "Preparation of Optically Active (R,R)-Hydrobenzoin from Benzoin or Benzil". Organic Syntheses : 10{{cite journal}}: CS1 maint: multiple names: authors list (link).
  6. Bolm, Carsten; Atodiresei, Iuliana; Schiffers, Ingo (2005). "Asymmetric Alcoholysis of Meso-Anhydrides Mediated by Alkaloids". Organic Syntheses. 82: 120. doi:10.15227/orgsyn.082.0120.
  7. Wilent, Jennifer; Qabaja, G.; Petersen, K. S. (2016). "Enantioselective Synthesis of α,α-Disubstituted Lactones via a Chiral Brønsted Acid Catalyzed Intramolecular Cyclization". Organic Syntheses. 93: 75–87. doi:10.15227/orgsyn.093.0075. PMC   5198840 . PMID   28042185.
  8. Basic Terminology of Stereochemistry, G.P. Moss Ed. Pure Appl. Chem., Vol. 68, No. 12, pp. 2193-2222, 1996.