X- (X=I, Br) 誘発の環開き結合反応で,サイクロプロペンが有機ハリド化物と結合する
Shengming Ma1, Junliang Zhang, Yangjun Cai
1State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P.R. China.
Journal of the American Chemical Society
|November 13, 2003
まとめ
新しいリング開き結合反応により,多機能化 (E) -アルク-1-エニルハリドが効率的に合成されます. この新しい方法は,サイクロプロペンと有機ハリドを使用し,高収量と貴重な化学化合物の優れた地域およびステレオ選択性を提供します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 合成化学 合成化学とは
背景:
- サイクロプロペンは,独特の反応性を有するストレントサイクルアルケーンである.
- 機能化されたアルケンを合成するための効率的な方法の開発は,有機合成において極めて重要です.
研究 の 目的:
- 多機能化 (E) -アルク-1-エニルハリドを合成するための新しく効率的な方法を開発する.
- オーガニックハライドとサイクロプロペンの地域およびステレオ選択的リング開き結合を調査する.
主な方法:
- 新しいX- (X = I または Br) 誘発のリング開き結合反応.
- 原材料として利用されたサイクロプロペン (1) と有機ハリド (2) です.
主要な成果:
- 多機能化 (E) -アルカリ-1-エニルハリドの効率的な合成 (3) 高収量.
- この反応は,高い地域およびステレオ選択性を示した.
- 新型カップリング戦略の成功した適用.
結論:
- 開発された環開き結合反応は,複雑な (E) -アルク-1-エニルハライドを構成する強力なツールです.
- この方法は,重要な有機中間産物への貴重な合成経路を提供します.
- 高い効率性と選択性は,合成化学者に大きな利点をもたらします.
関連する概念動画
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
02:41Formation of Halohydrin from Alkenes
An alkene, such as propene, reacts with bromine in the presence of water to yield a halohydrin. Halohydrins contain a halogen and a hydroxyl group attached to adjacent carbons. When the halogen is bromine, it is called a bromohydrin, while a chlorohydrin has chlorine as the halogen.
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...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:14Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.