Co (III) コンプレックスを持つアジリジンのステレオセレクティブ認識:触媒エポキシデーションのための潜在的な移行状態アナログ
Rhiana Bobb1, Gamil Alhakimi, Lisa Studniki
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
Journal of the American Chemical Society
|April 25, 2002
まとめ
この研究では,サレンのリガンドを持つコバルト (III) 複合体は,キラルアジリジンを選択的に結合することを示しています. (S,S) コバルト (III) 複合体は,アジリジンとより強い結合を示し,ステレオ選択的認識機構を明らかにします.
科学分野:
- 協調化化学について
- ステレオセレクティブ合成
- 有機金属化学 有機金属化学
背景:
- チラルアジリジンは,価値ある合成中間物質である.
- サレンリンガンドは,非対称な触媒で広く使用されています.
- ステレオ選択的調整を理解することは,触媒設計において極めて重要です.
研究 の 目的:
- キラルアジリジンからコバルト (III) コンプレックスへのステレオ選択的調整を調査する.
- (S,S) L-Co (III) 複合体と (R,R) L-Co (III) 複合体の結合偏好を明らかにする.
- ステレオ選択的認識の構造的基礎についての洞察を得るために.
主な方法:
- コバルト ((III) コンプレックスとサレントリガンドの合成.
- 1H NMRスペクトル検査で結合親和性を評価する.
- 調整構造を決定するためのX線結晶学.
- 構造分析のための分子力学の計算.
主要な成果:
- 1-(R) -フェニル-2-(S) -メチラジリジンの可逆性およびステレオ選択的調整が観察されました.
- (S,S) L-Co (III) 複合体は, (R,R) L-Co (III) 複合体と比較して,アジリジンとの結合が約3倍強かった.
- クリスタル構造は,アジリジンのコバルト (III) センターへの正確な調整モードを明らかにしました.
結論:
- この研究は,キラルアジリジンとコバルト (III) -塩素複合体の間の有意なステレオ選択的認識を示しています.
- 構造的および計算的データは,観察された選択性の分子レベルの理解を提供します.
- これらの発見は,非対称合成のためのキラル触媒の開発に寄与します.
関連する概念動画
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
Oxidation 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.
Preparation 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...
Sharpless 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...
Acid-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...
Base-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...


