Stereoselective transannular radical cyclization of unsaturated cyclic iodoacetals yielding medium-sized carbocycles

Iodoacetalization of (Z)-allylic alcohols 1a-1c in high dilution followed b y transannular radical cyclization gave cis-fused bicyclic acetals 5a-5c an d 6a-6c with high diastereoselectivities (84-93% de) and in 54-62% yields. The reaction of 2a gave 5a and ba with 77% de, but in low yield. However, t he sequential reaction of the higher homologue 1d and (E)-allylic alcohols 2b-2d showed poor diastereoselectivities.