Photoexcited cobalt catalysed endo -selective alkyl Heck reaction.

Herein, we report an intramolecular endo -selective Heck reaction of iodomethylsilyl ethers of phenols and alkenols. The reaction leads to the formation of seven- and eight-membered siloxycycles in excellent yields, which could be further converted into the corresponding allylic alcohols upon oxidation. Thus, this method could be used for the selective ( Z )-hydroxymethylation of o -hydroxystyrenes and alkenols. Rapid scan EPR experiments and DFT calculations suggest a concerted β -hydrogen elimination event to take place in the triplet state.