Synthesis of 2‐Aminopyridines via Cobalt‐Catalyzed Cycloaddition of Diynes with N‐Substituted and N‐Unsubstituted Cyanamides

Abstract

Reactivity of nitriles in a CoCl<sub>2</sub>‐6H<sub>2</sub>O/dppe/Zn–catalyzed diyne–nitrile cycloaddition was explored through the competitive reactions of a diyne with two different nitriles, and it was found that cyanamides are good substrates, and the reaction yielded 2‐aminopyridines. Notably, N‐unsubstituted cyanamide (H<sub>2</sub>N–CN) could be used for the reaction with 1,6‐diynes to afford the corresponding <i>N</i>‐unsubstituted 2‐aminopyridines, which cannot be prepared via other catalytic reactions and are versatile intermediates for further transformations such as the synthesis of 2‐substituted pyridines and 6,7‐annulated imidazo[1,2‐a]pyridines.