黄金 (((I) 催化立体选择性烯循环化
Magnus J Johansson1, David J Gorin, Steven T Staben
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|December 22, 2005
概括
一种新型的黄金 (I) 复合物催化了使用甲基的烯酸环化. 这种方法可以有效地产生具有高恩选择性和cis选择性的乙烯基环烯酸.
科学领域:
- 有机金属化学 有机金属化学
- 不对称的催化剂.
背景情况:
- 金 ((I) 复合物是碳转移反应的有效催化剂.
- 甲基可以作为黄金 (I) - 碳化合物的前体.
研究的目的:
- 开发一种由黄金 (I) 催化的烯酸环化.
- 为了实现乙烯基环烯酸乙烯的酶选择性合成.
主要方法:
- 三酸黄金 (((I) -催化循环化反应.
- 作为黄金 (I) - 碳基的前体,使用了propargy Ester.
- 采用DTBM-SEGPHOS金 ((I) 复合物进行反选择性催化.
主要成果:
- 成功地实现了olefins的循环化.
- 通过DTBM-SEGPHOS gold ((I) 催化剂实现了对抗选择性乙烯基环胺的合成.
- 获得了高反体过量 (高达94% ee) 和cis选择性.
结论:
- 建立了一种新且高效的金催化环化方法.
- 开发的协议提供了访问有价值的乙烯基环烯衍生物.
- 在这种转换中,DTBM-SEGPHOS连接体对于实现高立体选择性至关重要.
相关概念视频
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
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.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
01:22Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...