阴离子 ((I) 复合催化 [3 + 2] 和 [2 + 1] 循环添加与缺电子基和基的propargyl基
Yu Shibata1, Keiichi Noguchi, Ken Tanaka
1Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
Journal of the American Chemical Society
|May 22, 2010
概括
一个阴离子 ((I) 复合物有效地催化了两个不同的循环添加反应. 它促进了 [3+2] 循环添加的propargyl 和 [2+1] 循环的高产量和选择性.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 有机合成 有机合成
背景情况:
- ((I) 复合物是有机转化中的多功能催化剂.
- 循环添加反应对于构建循环有机分子至关重要.
- 甲基 Ester 是一种有价值的合成构建块.
研究的目的:
- 为了研究一个阴离子 () 复合体的催化活性,[Rh () ]SbF () 6).
- 探索其在 [3+2] 循环添加反应中的应用.
- 为了检查它在 [2+1] 循环化反应中的有用性.
主要方法:
- 采用一个阴离子 ((I) 复合物, (Rh ((cod) ((2)) ]SbF ((6),作为催化剂.
- 与dialkyl acetyleneedicarboxylates对 [3+2] 循环添加进行反应的propargyl .
- 与N,N-异位的烯胺反应的propargyl Ester,用于 [2+1] 循环化.
主要成果:
- ((I) 复合物有效催化了甲基乙烯基碳酸盐和甲基乙烯基碳酸盐的 [3+2] 循环添加,使产品产生了良好的产量.
- 同一个催化剂促进了与N,N-非替代烯胺的甲基的 [2+1] 循环添加 (cyclopropanation).
- 循环化反应以完美的二元体选择性进行.
结论:
- 阴离子 ((I) 复合物是 [3+2] 和 [2+1] 循环添加反应的有力催化剂.
- [3+2]循环添加的催化机制可能涉及碳结合稳定型阴离子 ((I) 基碳中间体.
- 这项研究突出了一个新的合成途径,用于构建高效率和选择性复杂的有机分子.
相关概念视频
Electrophilic 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.
Reduction 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.
Electrophilic 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.
Preparation 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.
Alkynes 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.
Cycloaddition 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.


