催化3 - 乙-1,4-乙烯和的分子内和分子间 [5 + 2] 循环添加与同时发生的1,2-乙迁移
Xing-Zhong Shu1, Xiaoxun Li, Dongxu Shu
1School of Pharmacy, University of Wisconsin, Madison, Wisconsin 53705, United States.
Journal of the American Chemical Society
|February 28, 2012
概括
一种新型的催化 [5 + 2] 循环添加反应有效地合成了多种多样的七分环. 这种方法涉及3-基-1,4-基 (ACE) 和基,具有独特的1,2-基迁移.
科学领域:
- 有机化学 有机化学
- 催化剂是一种催化剂.
- 合成方法论 合成方法论
背景情况:
- 七条环是药物化学和材料科学中的重要支架.
- 有效的合成路径,以功能化七个成员的环仍然是一个挑战.
- 催化为复杂分子构建提供了独特的途径.
研究的目的:
- 开发一种新的催化 [5 + 2] 循环添加反应.
- 为了合成具有1,2-乙氧迁移的多种七分环.
- 探索分子内和分子间的反应途径.
主要方法:
- 使用 () 催化剂,包括阴离子和中性复合物.
- 采用3-基-1,4-基 (ACE) 作为五碳组成部分和基作为两碳组成部分.
- 研究了缺乏电子的酸盐和酸盐联体对反应效率的影响.
主要成果:
- 成功开发了一种催化 [5 + 2] 循环添加反应.
- 通过分子内和分子间途径实现了七个成员环的高效合成.
- 证明了与各种ACE和基的反应的多功能性.
- 观察到伴随环形形成的1,2-乙氧迁移.
- 产生的产品有三个双键,可接受选择性功能化.
结论:
- 建立了一个新的,高效的催化 [5 + 2] 循环添加,用于七个成员的环合成.
- 反应过程以一种独特的1,2-乙氧迁移进行,提供了进入复杂结构的途径.
- 开发的方法提供了一个多功能平台,用于构建功能化的七分环,在各种化学领域具有潜在的应用.
相关概念视频
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
01:16Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
02:35Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.