Copper-Catalyzed Oxidative [3 + 2] Cycloaddition of N-Alkyl Pyridinium Salts to Imidazo[1,2-a]pyridines
Yuan Zhang1,2, Weibin Fan1, Yinghua Li1
1State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
Abstract:
A copper-catalyzed reaction of pyridinium salts and trimethylsilyl cyanide (TMSCN) in the presence of diethyl phosphite is developed. This reaction, which allows the single-step construction of biologically important 2-cyanoimidazo[1,2-a]pyridine from readily available starting materials, is realized for the first time and is feasible at the gram scale. The scope of the protocol is demonstrated with 27 examples. A consecutive double cyanation and cyclization can be achieved in this one-pot process. TMSCN plays a dual role not only as the "CN" source but also as the coupling partner for the cyclization of imidazo[1,2-a]pyridines.
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