Divergent Palladium-Catalyzed Cross-Coupling of Nitropyrazoles with Terminal Alkynes

Facile homo-coupling of terminal alkynes, which generates conjugated diynes, is an undesired pathway in the development of transition-metal-catalyzed oxidative C–H functionalization of (hetero)arenes with terminal alkynes. By incorporating this process into a catalytic cycle, we achieved regio- and stereoselective hydroarylation of nitropyrazoles with the resulting 1,3-diynes. A simple change in the stoichiometry and oxidant allowed direct C–H alkynylation of nitropyrazoles, producing the corresponding alkynyl pyrazoles.