メタルポルフィリンによって触媒化された地域選択的およびエナチオ選択的エポキシデーション
J P Collman1, X Zhang, V J Lee
1Department of Chemistry, Stanford University, CA 94305.
Science (New York, N.Y.)
|September 10, 1993
まとめ
メタロポルフィリン触媒は,精密な地域選択性およびエナチオ選択性エポキシデーションを可能にします. このレビューは,バイオミメティック起源と合成の関連性をカバーし,パフォーマンスの向上のために体系的に変更可能な触媒システムを強調します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
- バイオミメティック化学
背景:
- メタロポルフィリンは生物学的酸化プロセスにおいて極めて重要です.
- エポキシデーション反応は,複雑な有機分子を合成するために不可欠です.
- バイオミメティックアプローチは,天然の触媒機能を複製することを目的としています.
研究 の 目的:
- メタルポルフィリン触媒によるエポキシデーションにおける最近の進歩をレビューする.
- これらの触媒の生体模倣的起源と合成的有用性について議論する.
- 将来の改善のための触媒開発を分類し,分析する.
主な方法:
- リージオ選択的およびエナチオ選択的エポキシデーションに関する文献レビュー.
- メタルポルフィリン触媒の構造と改変の分析.
- 性能と合成アクセシビリティに基づいた触媒の分類.
主要な成果:
- メタルポルフィリンを用いたレジオ選択的およびエナチオ選択的エポキシデーションにおいて,著しい進展がみられた.
- 系統的に変更可能なシステムから派生した触媒は,大きな希望を示しています.
- バイオミメティックと実用的なアプリケーションの両方が,これらの進歩から利益を得ています.
結論:
- メタロポルフィリン触媒は,選択的エポキシデーションのための強力なツールを提供します.
- 系統的な合成改変は,優れた触媒の開発の鍵である.
- この分野は,合成有機化学の応用に相当な関連性を持っています.
関連する概念動画
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
02:57Sharpless Epoxidation
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
02:24Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
02:26Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
01:33Regioselective Formation of Enolates
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.