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电催化Csp3-Csp3双脱碳合
Benxiang Zhang1, Yang Gao1, Yuta Hioki1
1Department of Chemistry, Scripps Research, La Jolla, CA, USA.
Nature
|April 5, 2022
概括
通过使用温和的电催化系统将两种不同的碳酸盐连接起来,使得新的碳-碳键形成. 通过克服传统方法的局限性, 这促进了有机合成.
科学领域:
- 有机化学
- 电化学
- 催化剂
背景情况:
- 碳-碳键的形成对于合成复杂分子至关重要.
- 科尔贝电解是一种古老的Csp3-Csp3结合反应,由于恶劣的氧化条件,其作用范围有限.
- 传统的方法在范围和功能组宽容方面存在局限性.
研究的目的:
- 开发一种使用碳酸盐形成C-C键的更温和,更通用的方法.
- 克服传统的科尔贝电解和交叉电友合的局限性.
- 通过一种新的交叉合策略来实现复杂分子的合成.
主要方法:
- 开发一种轻度还原的电催化系统.
- 使用在位生成的碳酸盐的氧化还原活性.
- 使用双脱碳交叉合用于异构合.
主要成果:
- 成功合初级,二级和三级氧化还原活性.
- 证明了一种双重脱碳交叉合的新方法.
- 合成32种已知化合物的总步骤数量减少了73%.
- 反应可以承受广泛的功能组,并且可扩展.
结论:
- 电催化系统为C-C键形成提供了一种强大的新方法.
- 这种方法扩大了碳酸盐在有机合成中的合成效用.
- 双脱碳交叉合为现有方法提供了一种操作上简单且高效的替代方案.
相关概念视频
01:27Vicinal Diols via Reductive Coupling of Aldehydes or Ketones: Pinacol Coupling Overview
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Wilhelm Rudolph Fittig discovered the pinacol coupling reaction in 1859. It is a radical dimerization reaction and involves the reductive coupling of aldehydes or ketones in the presence of hydrocarbon solvent to yield vicinal diols.
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01:22Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
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Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
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01:17Thermal Electrocyclic Reactions: Stereochemistry
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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.
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01:26Thermal and Photochemical Electrocyclic Reactions: Overview
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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.
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01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
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Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
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01:26Photochemical Electrocyclic Reactions: Stereochemistry
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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
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