Studies on anticoccidial agents. 11. Synthesis and anticoccidial activity of nitropyridinecarboxamides and derivatives.

Of the nine nitropyridinecarboxamides, which are isomers of 5-nitronicotinamide, a potent anticoccidial agent, 2-nitropyridine-3, -4, -5-, or 6-carboxamides and 3-nitropyridine-4- or 6-carboxamides were prepared from the corresponding acids via the esters of the acid chlorides. 3-Nitropyridine-2-carboxamide was obtained from 2-methyl-3-nitropyridine by oxidation with SeO2, oximation, dehydration with Ac2O, and hydrolysis with H2SO4. 4-Nitropyridine-2-carboxamide was prepared from 2-cyano-4-nitropyridine by hydrolysis, and the 3-carboxamide analogue was obtained from 4-amino-3-cyanopyridine by oxidation with H2O2 and fuming H2SO4. Of these compounds 2-nitro- and 3-nitro- but not 4-nitropyridinecarboxamides were found to be active against Eimeria tenella. N-Substituted analogues of 2-nitro- and 3-nitropyridine carboxamides were also prepared in a conventional manner and optimal anticoccidial activity was attained with 2-nitroisonicotinamide and its N-alkanoyl, N-aromatic, and N-heterocyclic acyl derivatives.