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Pericyclic Reactions: Cycloadditions and Diels-Alder Reaction

Cycloadditions: 1,3-Dipolar Cycloadditions

1,3-Dipolar cycloadditions represent synthetically important reactions for the preparation of heterocyclic five-membered rings. They belong into the group of [4+2] cycloadditions according to the Woodward-Hoffmann classification.


The 1,3-dipolar compounds contribute four electrons to the reaction, therefore their structural formulae can only be described by indicating formal charges.


The mechanism of alkene ozonolysis is a sequence of 1,3-dipolar cycloadditions and cycloreversions.


2D Animation of ozonolysis

3D Animation of ozonolysis

Movie of ozonolysis

Additional examples:

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