Iodohexene Radical Cyclisation Exo

NOTE: Important charges and non-bonding electrons are shown throughout the animation except during the transition state phase.

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This method is commonly used to make five membered rings. This is due to the selectivity of smaller ring sizes over bigger sizes. The reaction proceeds via an abstraction of iodine by a trimethyltin radical. The chain can then twist into a position to cyclise. The abstraction of hydrogen from trimethyltinhydride by the methylcyclopentane radical to form the exo product is not shown.

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Back Radical Cyclisation Summary

H. Fischer and L. Radom, Angew. Chemie Int. Ed., 2001, 40, 1340–1371.