Microwave Assisted Hydrogenation of Pyridinecarboxylates: a Convenient Access to Valuable Scaffolds for Diversity Oriented Synthesis

Hydrogenation of pyridine under Microwave (MW) dielectric heating is a valuable method for a rapid approach to piperidine synthesis. Starting from easily available pyridinecarboxylate derivatives, aminopipecolic scaffolds were prepared and further decorated with a procedure potentially useful for parallel synthesis. MW hydrogenation on PtO2 proceeded with high stereoselectivity and low catalyst loading under mild conditions (80°C and 850 MPa of H2 pressure). MWs were also effective to perform a Pinner reaction on 2-cyano-nitropyridines to obtain the corresponding methyl nitropyridine carboxylates. A general procedure to decorate the 3-, 4-, and 5-amino-pipecolic derivatives obtained from the pyridine hydrogenation has been also developed.