Selective Approach toward Multifunctionalized Lactams by Lewis Acid Promoted PhSe Group Transfer Radical Cyclization

We have developed a regiospecific and highly stereoselective strategy for constructing the five-/six-membered monocyclic and bicyclic nitrogen heterocycle skeletons using PhSe group transfer radical cyclization of α-phenylseleno amido esters promoted by a Lewis acid (e.g., Yb(OTf)<sub>3</sub>) under UV irradiation. We obtained 5-/6-<i>exo-trig</i> mode cyclization products for the <i>N</i>-allyl/homoallyl substrates, whereas the enamide substrate gave 5-<i>endo-trig</i> ring closure.