Synthesis of 2-aminopyridines via ruthenium-catalyzed [2+2+2] cycloaddition of 1,6- and 1,7-diynes with cyanamides: scope and limitations

Abstract

A practical and mild process to access 2-aminopyridine derivatives using ruthenium-catalyzed [2+2+2] cycloaddition of various 1,6- and 1,7-diynes with cyanamides is described. This straightforward atom-economical catalytic cycloaddition is scalable and showed excellent regioselectivities to approach a wide range of 2-aminopyridines of high synthetic utility. Postfunctionalization reactions of halo-containing adducts, via Pd- and Cu-catalyzed cross-couplings as well as cyanation and amination reactions, delivered substituted 2-aminopyridine derivatives in good to excellent yields.