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相关概念视频

Preparation of Epoxides03:00

Preparation of Epoxides

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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...
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Base-Catalyzed Ring-Opening of Epoxides02:26

Base-Catalyzed Ring-Opening of Epoxides

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Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
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Acid-Catalyzed Ring-Opening of Epoxides02:24

Acid-Catalyzed Ring-Opening of Epoxides

7.0K
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...
7.0K
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation02:47

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

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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.
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Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

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Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
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Sharpless Epoxidation02:57

Sharpless Epoxidation

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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...
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Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
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在可见光诱导的C-H化中使用环氧化物

Kurt Bentley1, Mishra Deepak Hareram1, Gang-Wei Wang1,2

  • 1Department of Chemistry, School of Natural Science, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.

Journal of the American Chemical Society
|February 4, 2025
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概括

光激发的双环化复合物 (BCRCs) 显示出对C-H功能化的增强反应性. 这一发现使新的基化反应与环氧化物,扩大催化化学.

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科学领域:

  • 有机金属化学
  • 摄影化学
  • 催化剂

背景情况:

  • 类型[Ru(N^C) 2L2]的双环化复合物 (BCRC) 是Ru(II) 催化定向C-H功能化的关键中间体.
  • BCRC与电友的基态反应性已得到充分证实,但它们在光激发后的行为仍未被探索.

研究的目的:

  • 研究BCRC的光激发及其进入化学有用激发状态的潜力.
  • 在化激活过程中探索光激 BCRC 的反应性.
  • 扩大Ru催化C-H功能化的范围,包括新的转换.

主要方法:

  • 对二氨酸复合物 (BCRC) 的光刺激研究.
  • 研究基化物激活的电子转移过程.
  • 在C-H功能化反应中应用光激发的BCRC.

主要成果:

  • 通过BCRC的光激发,可以成功进入化学相关的激发状态.
  • 与基态相比,光激发的BCRC在电子转移过程中表现出显著增强的反应性.
  • 这种增强的反应能力克服了基态催化C-H功能化的限制.

结论:

  • 通过电子转移激发的BCRC提供了激活基化物的新途径.
  • 这项研究扩大了Ru-催化C-H功能化的化学空间,特别是通过环氧化物实现了正基化.
  • 这项工作突显了光化学在有机金属催化中释放新型反应的潜力.