epoxide

エポキシド

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/10/16 04:49:19」(JST)

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A generic epoxide.

An epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in chloromethyloxirane. As a functional group, epoxides feature the epoxy prefix, such as in the compound 1,2-epoxycycloheptane, which can also be called cycloheptene epoxide, or simply cycloheptene oxide.

The chemical structure of the epoxide glycidol, a common chemical intermediate

A polymer formed by reacting epoxide units is called a polyepoxide or an epoxy. Epoxy resins are used as adhesives and structural materials. Polymerization of an epoxide gives a polyether, for example ethylene oxide polymerizes to give polyethylene glycol, also known as polyethylene oxide.

Synthesis

The dominant epoxides industrially are ethylene oxide and propylene oxide, which are produced respectively on the scales of approximately 15 and 3 million tonnes. The epoxidation of ethylene involves its catalytic reaction of oxygen according to the following stoichiometry:

7 H₂C=CH₂ + 6 O₂ → 6 C₂H₄O + 2 CO₂ + 2 H₂O

The direct reaction of oxygen with alkenes is useful only for this epoxide. Other alkenes fail to react usefully, even propylene.

Olefin peroxidation

Most epoxides are generated by treating alkenes with peroxide-containing reagents, which donate a single oxygen atom. Typical peroxide reagents include hydrogen peroxide, peroxycarboxylic acids (generated in-situ or preformed), and alkyl hydroperoxides. In specialized applications, other peroxide-containing reagents are employed, such as dimethyldioxirane.

The largest scale application of this approach is the production of propylene oxide from propylene using either t-butyl hydroperoxide or ethylbenzene hydroperoxide. More typically for laboratory operations, the Prilezhaev reaction is employed. This approach involves the oxidation of the alkene with a peroxyacid such as m-CPBA. Illustrative is the epoxidation of styrene with perbenzoic acid to styrene oxide:

The reaction proceeds via what is commonly known as the "Butterfly Mechanism." The peroxide is viewed as an electrophile, and the alkene a nucleophile. The reaction is considered to be concerted (the numbers in the mechanism below are for simplification).

Hydroperoxides are also employed in catalytic enantioselective epoxidations, such as the Sharpless epoxidation and the Jacobsen epoxidation. In such cases, the oxygen is delivered from a metal oxide or peroxide. Together with the Shi epoxidation, these reactions are useful for the enantioselective synthesis of chiral epoxides. Oxaziridine reagents may also be used to generate epoxides from alkenes.

Intramolecular S_N2 substitution

This method is a variant of the Williamson ether synthesis. In this case, an alkoxide ion displaces a chloride atom within the same molecule. The precursor compounds are called halohydrins. For example, with 2-chloropropanol:

Approximately half of the world's supply of propylene oxide arises via this route. An intramolecular epoxide formation reaction is one of the key steps in the Darzens reaction.

In the Johnson–Corey–Chaykovsky reaction epoxides are generated from carbonyl groups and sulfonium ylides. In this reaction, a sulfonium is the leaving group instead of chloride.

Nucleophilic epoxidation

Electron-deficient olefins, such as enones and acryl derivatives can be epoxidized using nucleophilic oxygen compounds such as peroxides. The reaction is a two-step mechanism. First the oxygen performs a nucleophilic conjugate addition to give a stabilized carbanion. This carbanion then attacks the same oxygen atom, displacing a leaving group from it, to close the epoxide ring.

Asymmetric epoxidation

The carbon atoms of an epoxide are approximately sp³-hybridized, and thus may be stereogenic positions. Depending on the mechanism of the reaction and the geometry of the alkene starting material, cis and/or trans epoxide diastereomers may be formed. In addition, if there are other stereocenters present in the starting material, they can influence the stereochemistry of the epoxidation relative to them. This diastereoselectivity is a form of "substrate control" of the reaction. Finally, epoxidizing agents that possess stereogenic structures can influence the stereochemistry of the epoxide product (see for example the Sharpless epoxidation, Jacobsen epoxidation, Waits–Scheffer epoxidation, and Juliá–Colonna epoxidation). This enantioselectivity is a form of "reagent control" of the reaction.

Reactions

Typical epoxide reactions are listed below.

• Nucleophilic addition to an epoxide can be base or acid catalyzed.

• Under acidic conditions, the position the nucleophile attacks is affected both by steric effects (as normally seen for S_N2 reactions) and by carbocationic stability (as normally seen for S_N1 reactions). Under basic conditions, the nucleophile attacks the least substituted carbon, in accordance with standard S_N2 nucleophilic addition reaction process.

• Hydrolysis of an epoxide in presence of an acid catalyst generates a glycol. The hydrolysis process of epoxides can be considered to be the nucleophilic addition of water to the epoxide under acidic conditions.
• Reduction of an epoxide with lithium aluminium hydride and water generates an alcohol. This reduction process can be considered to be the nucleophilic addition of hydride (H-) to the epoxide under basic conditions.

• Reduction with tungsten hexachloride and n-butyllithium generates the alkene. This reaction in effect is a de-epoxidation:

• Reaction with the NH group in an amine. This covalent bond formation is utilised in epoxy glue with, e.g., Triethylenetetramine (TETA) as a hardener.

Perepoxides

Perepoxides are epoxides with an additional oxygen atom attached to the epoxide-oxygen. They are isoelectronic and isostructural with the cyclic sulfoxides derived from episulfides. Perepoxides are proposed intermediates in the photosensitized oxidation of alkenes, as occurs when drying oils (a component of some paints and varnishes) are exposed to air in light. Such intermediates arise from the addition of singlet oxygen to the double bond. Perepoxides rapidly rearrange to allylic hydroperoxides.

See also

• Polyether
• Epoxide hydrolase
• Juliá–Colonna epoxidation
• Johnson–Corey–Chaykovsky reaction

References

UpToDate Contents

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• 1. ビタミンＫとγカルボキシグルタミン酸の合成および機能 vitamin k and the synthesis and function of gamma carboxyglutamic acid
• 2. ビタミンKの概要 overview of vitamin k
• 3. 薬理ゲノム学の概要 overview of pharmacogenomics
• 4. ワルファリンおよびその他のビタミンK拮抗剤の治療使用 therapeutic use of warfarin and other vitamin k antagonists
• 5. Biology of warfarin and modulators of INR control

English Journal

• Facile and fast synthesis of polyaniline-coated poly(glycidyl methacrylate) core-shell microspheres and their electro-responsive characteristics.

• Zhang WL, Piao SH, Choi HJ.SourceDepartment of Polymer Science and Engineering, Inha University, Incheon 402-751, Republic of Korea.
• Journal of colloid and interface science.J Colloid Interface Sci.2013 Jul 15;402:100-6. doi: 10.1016/j.jcis.2013.04.011. Epub 2013 Apr 19.
• Electro-responsive core-shell structured particles were fabricated in two steps. In the first step, a spherical and monodisperse poly(glycidyl methacrylate) (PGMA) core was prepared by dispersion polymerization with an epoxy group, which was then functionalized with an amine functional group (ami-PG
• PMID 23664394

• Discovery of 1-(1,3,5-triazin-2-yl)piperidine-4-carboxamides as inhibitors of soluble epoxide hydrolase.

• Thalji RK, McAtee JJ, Belyanskaya S, Brandt M, Brown GD, Costell MH, Ding Y, Dodson JW, Eisennagel SH, Fries RE, Gross JW, Harpel MR, Holt DA, Israel DI, Jolivette LJ, Krosky D, Li H, Lu Q, Mandichak T, Roethke T, Schnackenberg CG, Schwartz B, Shewchuk LM, Xie W, Behm DJ, Douglas SA, Shaw AL, Marino JP Jr.SourceDepartment of Chemistry, Heart Failure Disease Performance Unit, Metabolic Pathways and Cardiovascular Therapeutic Area Unit, GlaxoSmithKline, 709 Swedeland Road, King of Prussia, PA 19406, United States.
• Bioorganic & medicinal chemistry letters.Bioorg Med Chem Lett.2013 Jun 15;23(12):3584-8. doi: 10.1016/j.bmcl.2013.04.019. Epub 2013 Apr 16.
• 1-(1,3,5-Triazin-yl)piperidine-4-carboxamide inhibitors of soluble epoxide hydrolase were identified from high through-put screening using encoded library technology. The triazine heterocycle proved to be a critical functional group, essential for high potency and P450 selectivity. Phenyl group subs
• PMID 23664879

Japanese Journal

• The genetic mechanisms of warfarin resistance in Rattus rattus found in the wild in Japan

• Tanaka Kazuyuki D.,Kawai Yusuke K.,Ikenaka Yoshinori,Harunari Tsunehito,Tanikawa Tsutomu,Ando Shima,Min Hee Won,Okajima Fumie,Fujita Shoichi,Ishizuka Mayumi
• Pesticide Biochemistry and Physiology 103(2), 144-151, 2012-06
• … It inhibits blood coagulation by inhibiting vitamin K 2,3-epoxide reductase (VKOR) activity leading to hemorrhage. …
• NAID 120004405517

• Novel Cytotoxic Polyoxygenated Steroids from an Okinawan Sponge Dysidea sp.

• GOVINDAM Sudhakar V. S.,CHOI Bong-Keun,YOSHIOKA Yukio,KANAMOTO Akihiko,FUJIWARA Takeshi,OKAMOTO Tetsuji,OJIKA Makoto
• Bioscience, biotechnology, and biochemistry 76(5), 999-1002, 2012-05-23
• … A characteristic structural feature of 2, 4 and 5 is an allylic epoxide, whereas this epoxide undergoes ring-opening by a neighbouring hydroxyl group to give a tetrahydrofuran ring in 1 and 3. … All compounds 1–5 exhibited a similar cytotoxic effect with IC50 values of 0.15–0.3 µM against human epidermoid carcinoma A431 cells, demonstrating that the allylic epoxide moiety was not responsible for this cytotoxic effect. …
• NAID 10030753103

• 二酸化炭素を用いたポリマー

• 中野 幸司,野崎 京子
• 高分子 61(4), 182-184, 2012-04-01
• NAID 10030169739

Related Links

• Epoxide | Define Epoxide at Dictionary.com

Epoxide definition, an organic chemical that contains a group consisting of an oxygen atom bound to two already connected atoms, usually carbon (epoxy group) See more. Thesaurus Translate Puzzles & Games Reference Blog ...

• epoxide - definition of epoxide by Medical dictionary

epoxide /epox·ide/ (ĕ-pok´sīd) an organic compound containing a reactive group resulting from the union of an oxygen atom with two other atoms, usually carbon, that are themselves joined together. epoxide [ĕ-pok´sīd] an organic ...

Related Pictures

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★リンクテーブル★

リンク元	「アラキドン酸」「エポキシド」「epoxy compound」「エポキサイド」
拡張検索	「chlordiazepoxide」「epoxide hydrolase」「epoxide hydrolases」「chlordiazepoxide hydrochloride」

「アラキドン酸」

　　[★]

英

arachidonic acid, arachidonate

同

5,8,11,14-エイコサテトラエン酸 5,8,11,14-eicosatetraenoic acid、5,8,11,14-イコサテトラエン酸 5,8,11,14-icosatetraenoic acid

関

脂肪酸、必須脂肪酸

• 炭素数が20で二重結合を4つ有する
• CH₃(CH₂)₄(CH=CHCH₂)₄(CH₂)₂COOH
• リノール酸から合成される
• アラキドン酸は細胞膜の中にホスファチジルイノシトールのC2エステルまたは他のリン脂質のエステルとして蓄えられる (FB.159)

ホスホリパーゼA₂の作用でアラキドン酸として遊離

機能

• エイコサノイドの前駆体 (FB.159)

ロイコトリエンやプロスタグランジンの前駆体

• prostanoid, leukotriene, epoxideの前駆体

prostanoid： cyclooxygenase pathway

leukotriene：lipoxygenase pathway

epoxide：cytochrome P-450 epoxygenase pathway

代謝

• アラキドン酸－(5-lipoxygenase)→5-HPETE
• アラキドン酸－(cyclooxygenase)→PGG₂

「エポキシド」

　　[★]

英

epoxide

• エポキシド (epoxide) は3員環のエーテルであるオキサシクロプロパン（オキシラン）を構造式中に持つ化合物の総称で、最も単純なものはエポキシエタンである。置換基として見る場合はエポキシ基と呼ばれる。化学工業、有機合成化学の分野において中間体として重要である。
• http://ja.wikipedia.org/wiki/%E3%82%A8%E3%83%9D%E3%82%AD%E3%82%B7%E3%83%89

• ex.

• Vitamin K epoxide

「epoxy compound」

　　[★]

• エ・キシ化合物

関

epoxide

「エポキサイド」

　　[★]

英

epoxide

関

エ・キシド

「chlordiazepoxide」

　　[★] クロルジアゼポキシド 　

「epoxide hydrolase」

　　[★] エポキシドヒドロラーゼ

「epoxide hydrolases」

　　[★] エポキシドヒドロラーゼ

「chlordiazepoxide hydrochloride」

　　[★] クロルジアゼポキシド