Nanoparticles of Cobalt for the Reversible (De)Hydrogenation and Oxidative Dehydrogenation of N-Heterocycles under Mild Conditions

Employing a same catalyst, the reversible acceptorless dehydrogenation-hydrogenation and oxidative dehydrogenation of N-heterocycles have rarely been explored in the literature. Herein, we synthesized an earth-abundant, cheap, and robust cobalt heterogeneous nanoparticles for the reversible hydrogenation and dehydrogenation of N-heterocycles as well as the oxidative dehydrogenation of N-heterocycles under mild reaction conditions, which makes it attractive for hydrogen storage purposes. Employing an easy-to-synthesize reusable catalyst, a library of N-heterocycles molecules was reversibly hydrogenated and dehydrogenated in the presence of several other reducible functional groups in good to excellent yields. Notably, the practical applicability of the protocol was demonstrated by the gram-scale synthesis of several N-heterocycles and the synthesis of a few biologically important molecules such as angustureine, galipinine, and aspernigerin. This inexpensive catalyst can be recycled up to five times without considerable loss of catalytic activity, and inductively coupled plasma mass spectrometry (ICP-MS) analysis of the filtrate showed only a trace amount of cobalt leaching. Several control experiments and kinetic studies were carried out to understand the reaction mechanism.