オレフィンの鉄触媒による非対称性オキシアミン化
Kevin S Williamson1, Tehshik P Yoon
1Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
Journal of the American Chemical Society
|July 17, 2012
まとめ
新しい鉄触媒により,アルケンの地域選択性およびエナチオ選択性酸素アミナ化が可能になり,アミノアルコールが生成されます. この方法は,銅触媒の補完的な地域化学を提供し,安価な金属によるステレオ化学を制御します.
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
- アシンメトリック・シンセシス
背景:
- アルケンの酸化は,有価な窒素を含む化合物の合成に不可欠です.
- オキシアミネーションのための効率的で選択的な触媒方法の開発は,有機合成における重要な課題です.
研究 の 目的:
- アルケンの地域選択的およびエナチオ選択的酸素アミネーションのための新しい鉄 (II) 触媒を開発する.
- 既存の銅触媒方法と比較して,鉄触媒反応の補完的な地域選択性を調査する.
- 合成されたオクサゾリジン産物の有用性を実証し,エナンチオ濃縮アミノアルコールを得ることができるようにする.
主な方法:
- 新しい鉄 (II) ビス (オキサゾリン) 複合体を触媒として使用した.
- オキシアミネーション反応の窒素と酸素源としてN-スルフォニルオキシジリジンを使用した.
- 触媒プロセスの地域選択性とエナチオ選択性を研究した.
- オクサゾリジン産物を操作して,自由アミノアルコールを生成した.
主要な成果:
- 鉄 (II) 触媒はアルケンの地域選択的およびエナチオ選択的オキシアミン化に成功しました.
- この反応により,オクサゾリジンの中間物質が産生され,それらは容易に高度にエナンチオ濃縮された自由アミノアルコールに変換された.
- 鉄触媒で観察された地域選択性は,銅 ((II) 触媒反応の補完的であった.
- 酵素濃縮1,2-アミノアルコールの両方のレジオアイソマーは,鉄と銅の触媒のどちらかを選択することで入手できます.
結論:
- 新しい鉄 (((II) 触媒は,アルケンの非対称性オキシアミン化のための効果的な経路を提供します.
- 鉄触媒化プロセスは,銅触媒化に補完的な地域選択性を提供し,多様なアミノアルコールの地域単体へのアクセスを可能にします.
- 安価な第1列の移行金属触媒の使用は,オキシジリジン媒介によるオキシアミネーション反応において制御された地域化学を可能にします.
関連する概念動画
02:44Oxidation 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.
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.
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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...
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...