Dehydrogenation of Hantzsch Dihydropyridines with Hetero-geneous Cobalt Oxide Catalyst Supported in N-Doped Acti-vated Carbon

Abstract

Hantzsch dihydropyridines represent an important source of hydrogen to be transfered to other un-saturated organic molecules, leading the formation of pyridine aromatic ring as driving force. The hydrogen transfer process was evaluated using 1,4-dyhydropyridines and heterogeneous cobalt cat-alyst supported over N-doped activated carbon. The 4-position of the dihydropyridine ring was sub-stituted with H (4a), Me (4b) and Ph (4c) groups, showing that only 1 reacted to yield the correspond-ing pyridine compound indicating that the presence of steric hindrance took place on the reaction. Additionally; three solvents –tetrahydrofuran (THF), acetone, and acetonitrile– were tested, showing reactivity only with unsaturated ones, but not with THF. This observation indicates that dihydro-pyridine works as hydrogen donor and solvent as hydrogen aacceptor in the hydrogen transfer pro-cess. Keywords: Hantzsch dihyropyridine; Heterogeneous cobalt oxide catalyst; Hydrogen transfer; Unsaturated solvents