フォトプロモートされたRu触媒による非対称なエアロビック硫化物の酸化とエポキシデーションは,プロトン伝送媒介体として水を用いて行われます
Haruna Tanaka1, Hiroaki Nishikawa, Tatsuya Uchida
1Department of Chemistry, Faculty of Science, Graduate School, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Journal of the American Chemical Society
|August 13, 2010
まとめ
ルテニウム-塩素複合体は,室温で可視光の下で,硫化物の酸化とオレフィンエポキシデーションを含む非対称な有酸素酸素伝達反応を触媒化する. この方法は,生物学的システムに効率的な代替案を提供し,陽子/電子の移転や犠牲の還元剤の必要性を回避します.
科学分野:
- 有機金属化学 有機金属化学
- アシンメトリック・カタリシス
- グリーン・ケミストリー 緑の化学
背景:
- 生物学的酸素原子移転反応には,複雑な陽子および電子移転システムがしばしば必要である.
- 環境条件下で分子酸素を用いた非対称な酸素原子移転のための効率的な触媒システムを開発することは,依然として課題です.
研究 の 目的:
- 触媒的非対称性有酸素酸素原子移転反応のための新しいRu(NO) -塩素複合体を開発する.
- 硫化物の酸化とエポキシジング反応におけるこれらの複合体の効率とエナチオセレクティブ性を調査する.
- 犠牲となる還元剤と複雑な生物学的機械の必要性を回避する反応機構を探求する.
主な方法:
- Ru(NO) -塩素複合体の合成と特徴付け.
- 硫化物の触媒的非対称酸化と,室温で可視光照射を用いたオレフィンのエポキシデーション.
- キラルクロマトグラフィを用いたエナチオ選択性決定.
主要な成果:
- Ru(NO) -塩素複合体は,非対称な有酸素酸素原子移転反応を効果的に触媒化した.
- 硫化物の酸化は,複合体2を用いて最大98%のエナンチオセレクティビティ (ee) を達成した.
- コンジュガドオレフィンのエポキシデーションは,複合体3を用いて76~92%のEEが得られました.
- 反応は,水の存在下での環境条件下で効率的に進行し,犠牲の還元剤を必要としなかった.
結論:
- 触媒的非対称な酸素原子移転反応は,Ru (NO) -塩素複合体を含む環境条件下で分子酸素を使用して達成できます.
- アクア・リガンドは,陽子伝達剤として作用し,酸素の活性化と循環を促進する可能性がある.
- この方法論は,従来の生物学的酸素転送プロセスと比較して,よりグリーンで,よりアクセシブルなアプローチを示しています.
関連する概念動画
Preparation and Reactions of Sulfides
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
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.
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.
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...
Reduction 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...
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...

