环加成反应
Sign in to saveAlso known as Cycloaddition reaction
thumb|261x261px|Non-ionic Cycloadditions In organic chemistry, a cycloaddition is a chemical reaction in which "two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity". The resulting reaction is a cyclization reaction. Many but not all cycloadditions are concerted and thus pericyclic. Nonconcerted cycloadditions are not pericyclic. As a class of addition reaction, cycloadditions permit carbon–carbon bond formation without the use of a nucleophile or electrophile.
Research
22,707 papers- Intramolecular cycloaddition of nitrones in total synthesis of natural products.Natural product reports · 2025
- Transition-Metal-Catalyzed Bioorthogonal Cycloaddition Reactions.Topics in current chemistry (Cham) · 2016
- Bioorthogonal Reactions Utilizing Nitrones as Versatile Dipoles in Cycloaddition Reactions.Chemical reviews · 2021
- Diels-Alder Cycloaddition to the Bay Region of Perylene and Its Derivatives as an Attractive Strategy for PAH Core Expansion: Theoretical and Practical Aspects.Molecules (Basel, Switzerland) · 2020
- Sydnone-alkyne cycloaddition: applications in synthesis and bioconjugation.Chemical communications (Cambridge, England) · 2017
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Wikidata facts
- Subclass of
- pericyclic reaction
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- Category:Cycloadditions
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- Cycloadditions
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Article · 中文
环加成反应（英文：Cycloaddition）是两个或多个不饱和化合物（或同一化合物的不同部分）结合生成环状化合物，并伴随有系统总键级数减少的化学反应。它可以是周环反应或非协同的。逆过程称为环消除反应。 环加成反应的两种主要类型是狄尔斯-阿尔德反应和1,3-偶极环加成反应。 根据前线轨道理论，两个分子之间的环加成反应符合以下几点： 1. * 环加成反应中起决定作用的是一个分子的HOMO与另一个分子的LUMO。电子在反应过程中，从一个分子的HOMO流入另一个分子的LUMO。这主要是由于的缘故，使得两个HOMO相互作用时体系的能量升高，而在LUMO与HOMO作用时体系能量降低，趋于稳定； 2. * 在形成新的σ键时，两个起作用的轨道必须发生同位相的重叠。同位相重叠使能量降低，互相吸引，而异位相重叠使能量升高，产生排斥作用； 3. * 相互作用的两个轨道能量必须接近，而且能量越接近，反应就越容易进行。这是因为能差的减小会使新形成的成键轨道能级降低，从而使体系的能量降低值增大，体系趋于稳定。
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