Functionalization of α-Aminonicotinonitrile: A New Entry for Synthesis of Pyrazolo[3,4-b]pyridine, Pyrido[2,3-d]pyrimidine, and 1,8-Naphthyridine Derivatives.

Functionalization of α-aminopyridine to a new series of pyridine and fused pyridine derivatives has been achieved via its reaction with a variety of readily available reagents. Pyridines 2 and 3 were formed via reaction of amino derivative 1 with formamide and triethyl orthoformate. Hydrolysis of pyridine with 60% H2SO4 afforded 2-oxonicotinamide 6 in 44% yield. Intermolecular cyclization of pyridine 1 with ethyl cyanoacetate, diethyl malonate and malononitrile afforded pyrazolo[3,4-b]pyridine 8, pyrido[2,3-d]pyrimidine 9 and 1,8-naphthyridine 13 in moderate yields (63–76%). [ABSTRACT FROM AUTHOR]