Facile 5-endo amidyl radical cyclization promoted by vinylic iodine substitution.

[reaction: see text] BF(3).OEt(2)-catalyzed atom-transfer radical addition of iodoacetamides to alkynes yielded the corresponding vinyl iodides, which upon treatment with (t)BuOCl and I(2) afforded gamma-lactam derivatives in moderate to good yield. The mechanism was proposed to be 5-endo amidyl radical cyclization, and vinylic iodine substitution provided the driving force for the cyclization.