Metal-Free [2 + 2 + 2] Cycloaddition of Ynamides with Nitriles to Construct 2,4-Diaminopyridines

We present a metal-free [2 + 2 + 2] cycloaddition of ynamides with nitriles that enables highly efficient access to 2,4-diaminopyridines. This catalytic protocol is more environmentally friendly and allows for a concomitant construction of C–C and C–N bonds between ynamides and nitriles, exhibiting excellent chemoselectivity, regioselectivity, and wide functional groups tolerance.