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16.15: Cycloaddition Reactions: Overview

JoVE Core
Organic Chemistry

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Cycloaddition Reactions: Overview

16.15: Cycloaddition Reactions: Overview

Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.


The feasibility of cycloaddition reactions under thermal and photochemical conditions can be predicted using a set of selection rules. If the total number of π electrons involved in the rearrangement is a multiple of 4n, the reaction is photochemically allowed. The reaction is thermally allowed if the total number of π electrons involved is 4n + 2.


Cycloaddition Reactions Synthesis Routes Cyclic Compounds Pericyclic Reactions Unsaturated Compounds New Bonds Diels-Alder Reaction [4 + 2] Cycloaddition [2 + 2] Cycloaddition Thermal Conditions Photochemical Conditions Selection Rules π Electrons

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