Site-Selective Copper-N-Heterocyclic Carbene-Catalyzed C(sp²)-C(sp) Cross-Coupling of Aryl Thianthrenium Salts

This work demonstrates Cu-NHC (NHC = N-heterocyclic carbene) catalyzed alkynylation of aryl thianthrenium salts via thiazol-2-ylidene ligands, achieving a Pd-free Sonogashira coupling with broad substrate compatibility and functional group tolerance. Late-stage pharmaceutical alkynylation and rare alkynylative C-H functionalization/ring-opening pathways are enabled. Thiazol-2-ylidenes, featuring a "half-umbrella"-shaped geometry, exhibit superior catalytic performance over traditional imidazol-2-ylidenes, underscoring their unique ligand efficacy. Cu-NHC catalysis enables the use of aryl thianthrenium salts as versatile electrophiles for diverse cross-couplings under mild conditions.