Nickel-Catalyzed Thiolative Cyclization of Cyclic Enynones under Visible-Light Irradiation: An Easy Access to 9-Sulfenyl-2,3-dihydrophenanthren-4(1 H )-ones

An efficient nickel-catalyzed thiolative addition–cyclization of conjugated cyclic enynones for the synthesis of 9-sulfenyl-2,3-dihydrophenanthren-4(1H)-ones is described. The reaction proceeds through a nickel-catalyzed hydrothiolation of cyclic enynones, followed by visible-light-induced intramolecular cyclization. This protocol tolerates both aromatic and aliphatic thiols, affording sulfur-containing dihydrophenanthrenes in good to high yields. The synthetic utility of the method is further demonstrated by converting the obtained products into valuable phenanthrene derivatives.