Copper-Catalyzed C(sp³)–S Bond and C(sp²)–S Bond Cross-Coupling of 2-(2-Iodobenzoyl) Substituted or 2-(2-Iodobenzyl) Substituted 1,2,3,4-Tetrahydroisoquinolines with Potassium Sulfide: Synthesis of Isoquinoline-Fused 1,3-Benzothiazine Scaffolds

The sulfuration reaction of 2-(2-iodobenzoyl) substituted, or 2-(2-iodobenzyl) substituted 1,2,3,4-tetrahydroisoquinolines with potassium sulfide proceeded in the presence of copper catalysts to give tetrahydroisoquinoline-fused 1,3-benzothiazine scaffolds in moderate to appropriate yields. This protocol provided an efficient and simple strategy to construct the corresponding benzothiazine derivatives via formation of C(sp 3 )–S bond and C(sp 2 )–S bond, which the C–S bonds formed via different routes in this reaction (traditional cross-coupling reaction via the cleavage of C–I bond and oxidative cross-coupling reaction via C(sp 3 )–H bond functionalization).