A review on the assembly of multi-substituted pyridines via Co-catalyzed [2 + 2 + 2] cycloaddition with nitriles

This review mainly focuses on the recent advances in Co-catalyzed [2 + 2 + 2] cycloaddition reaction of alkynes with nitriles to access multi-substituted pyridines. Meanwhile, brief mechanistic insights are also discussed to explain the observed regioselectivity.