Sulfur Incorporation: Copper-Catalyzed Cascade Cyclization of 1,7-Enynes with Metal Sulfides toward Thieno[3,4‑<i>c</i>]quinolin-4(<i>5H</i>)‑ones

A novel copper-catalyzed cascade cyclization of 1,7-enynes with metal sulfides is described. This sulfur-incorporation method provides straightforward access toward the important thiophene-fused quinolin-4­(<i>5H</i>)-one scaffold through cyclization and double C–S bond formation cascade, and the chemoselectivity of this 1,7-enyne cyclization toward 1,3,3a,9b-tetrahydrothieno­[3,4-<i>c</i>]­quinolin-4­(<i>5H</i>)-ones and 3,3a-dihydrothieno­[3,4-<i>c</i>]­quinolin-4­(<i>5H</i>)-ones can be controlled by varying the sulfur resources