Reusable Cobalt-Catalyzed Selective Transfer Hydrogenation of Azoarenes and Nitroarenes.

Herein, control transfer hydrogenation (TH) of azoarenes to hydrazo compounds is established employing easy-to-synthesize reusable cobalt catalyst using lower amounts of NH·HO under mild conditions. With this effective methodology, a library of symmetrical and unsymmetrical azoarene derivatives was successfully converted to their corresponding hydrazo derivatives. Further, this protocol was extended to the TH of nitroarenes to amines with good-to-excellent yields.