Radical Cyclisations

'Click' the different radical cyclisations to view the 3D models of each reaction:

Overall both of the examples below are very powerful reactions, often being used to make five- and six-membered rings. This is due to the preference of the smaller sized ring formation over bigger sizes. These smaller rings form faster producing the exo products despite the fact that upon forming the endo products a more stabilised radical is formed.

Iodohexene Radical Cyclisation Reaction

Iodoheptene Radical Cyclisation Reaction

The usual reagent is tributyltin hydride but the trimethyl version is shown to simplify the animations.

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