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相关概念视频

Preparation of Epoxides03:00

Preparation of Epoxides

Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Sharpless Epoxidation02:57

Sharpless Epoxidation

The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
Acid-Catalyzed Ring-Opening of Epoxides02:24

Acid-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...
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal 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.
Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal 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.
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical 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

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相关实验视频

Updated: Jul 6, 2026

Chemoselective Modification of Viral Surfaces via Bioorthogonal Click Chemistry
12:31

Chemoselective Modification of Viral Surfaces via Bioorthogonal Click Chemistry

Published on: August 19, 2012

聚类的新型人造循环酶:对 (-) - 染色醇, (+) -8 -epi-puupehedione 和 (-) -11'-脱氧二醇甲基乙烯的对抗选择性总合成.

Hideaki Ishibashi1, Kazuaki Ishihara, Hisashi Yamamoto

  • 1Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan.

Journal of the American Chemical Society
|September 10, 2004
PubMed
概括
此摘要是机器生成的。

研究人员开发了一种新型的人工循环酶催化剂,用于酶选择性循环反应. 这种新的催化剂有效地合成了带有色素骨架的多环,包括有价值的天然产品.

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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)
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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

Published on: June 20, 2014

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
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Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

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相关实验视频

Last Updated: Jul 6, 2026

Chemoselective Modification of Viral Surfaces via Bioorthogonal Click Chemistry
12:31

Chemoselective Modification of Viral Surfaces via Bioorthogonal Click Chemistry

Published on: August 19, 2012

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)
06:34

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

Published on: June 20, 2014

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
10:17

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Published on: February 7, 2019

科学领域:

  • 有机化学 有机化学
  • 催化剂是一种催化剂.
  • 自然产品的合成自然产品的合成

背景情况:

  • 复杂有机分子的酶选择合成仍然是化学中的一个重大挑战.
  • 具有骨架的多环类类化合物存在于具有生物活性的各种自然产品中.
  • 开发高效的催化系统对于获得这些有价值的化合物至关重要.

研究的目的:

  • 为了引入一种新的光学纯净的人造环酶催化剂.
  • 为了证明催化剂在2 - - - - - - - - - - - - - - - - - - - - - - - - - - 聚烯衍生物的酶选择性循环化中的有效性.
  • 为了合成关键的多环基基,带有色素骨架.

主要方法:

  • 一种新型人造环酶的合成:光学纯的3-o-fluorobenzyloxy-2-hydroxy-2'-(p-methoxybemzyl)-1,1'-binaphthyl.SnCl4.4.
  • 催化剂在2 - - 聚烯基衍生物的酶选择性循环化中的应用.
  • 合成的多环 terpenoid 产品的特征.

主要成果:

  • 人工循环酶有效催化了enantioselective循环反应.
  • 合成产生的多环烯酸具有 chroman 骨架.
  • 合成了关键的天然产品和中间体,包括 (-) - 染色醇, (+) -8 -epi-puupehedione,和 (-) -11'-deoxytaondiol甲基乙烯.

结论:

  • 开发的人造环酶是一种强大的工具,用于酶选择性合成.
  • 这种方法可以有效地获取含的多环 terpenoids.
  • 催化剂促进了重要的自然产品及其中间体的合成.