Nickel-Catalyzed Deaminative Sonogashira Coupling of Alkylpyridinium Salts Enabled by a New NN2 Pincer Ligand

Alkynes are amongst the most valuable functional groups in organic chemistry and widely used in chemical biology, pharmacy, and materials science. However, the preparation of alkyl-substituted alkynes still remains elusive. Herein, a novel transformation is disclosed that enables the coupling of terminal alkynes with alkylpyridinium salts under Ni-catalysis. Key to the success of this coupling was the development of a new and readily accessible amide-type pincer ligand. This ligand allows naturally abundant alkyl amines as alkylating agents in Sonogashira reactions for the first time, and leads to diverse alkynes in excellent yields under mild conditions. Salient merits of this chemistry include broad substrates scope and functional group tolerance, gram-scale synthesis, one-pot transformation, versatile late-stage derivatizations as well as the use of inexpensive pre-catalyst and readily available substrates. The high efficiency and strong practicability bode well for the widespread applications of this strategy in constructing functional molecules, materials, and fine chemicals.