Stannyl radicals intramolecular addition

Kim reported efficient radical cyclizations involving azides as radical traps (Scheme 8.33)7 This intramolecular amination process is efficient and proceeds via a 3,3-triazenyl radical that readily eliminates nitrogen to afford an aminyl radical. The use of (TMSlsSiH gives better results than BusSnH since azides are relatively inert toward tris(trimethylsilyl) silyl radicals. However, tin hydride can be used with alkyl iodides since the iodine atom abstraction by the stannyl radical is faster than its addition to the azide. 

A tin radical adds to alkynes or allenes to form vinyl radicals which react with intramolecular C=N bonds to give heterocycles.45-48 The addition of a tin radical to C=0 bond forms O-stannyl ketyl which affords a cyclic compound via intramolecular radical addition to C=C bond (Equation (8)).49... 

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