Nickel-Catalyzed [2+2+2] Cycloaddition of Alkyne-Nitriles with Alkynes Assisted by Lewis Acids: Efficient Synthesis of Fused Pyridines.Chemistry. 2016 Nov 14; 22(47):16765-16769.C
A Ni/BPh3 catalyzed [2+2+2] cycloaddition of alkyne-nitriles with alkynes has been developed, which provides an efficient route to fused pyridines under mild reaction conditions. Mechanistic studies indicate that an azanickelacycle via heterocoupling of an alkyne with a nitrile moiety is possibly formed as a key reaction intermediate. The Lewis acid catalyst is crucial to the successful transformation, which is suggested to promote the oxidative cyclization process.