Direct Heteroarylation of Tautomerizable Heterocycles into Unsymmetrical and Symmetrical Biheterocycles via Pd/Cu-Catalyzed Phosphonium Coupling

The direct cross-coupling of tautomerizable heterocycles with various unfunctionalized heteroarenes has been achieved through PyBroP-mediated and Pd/Cu-catalyzed sequential C–OH/C–H activation. The methodology allows a facile entry into novel diazine-azole biheterocyclic frameworks. Moreover, an unprecedented Pd-catalyzed phosphonium homocoupling of tautomerizable heterocycles was also developed to afford a direct synthetic route to symmetrical 1,2-, 1,3-, and 1,4-bidiazine units

Pd/Cu-Catalyzed C–H Arylation of 1,3,4-Thiadiazoles with (Hetero)aryl Iodides, Bromides, and Triflates

The direct C–H arylation of 1,3,4-thiadiazoles with a wide range of (hetero)­aryl iodides, bromides, and triflates is described using a Pd/Cu-catalyzed protocol. The methodology is compatible with substrates possessing electron-donating or electron-withdrawing substituents and also tolerates sterically hindered aryl halides. The utility of the developed protocol is demonstrated by a one-pot C–H arylation-Suzuki coupling sequence