v-Triazolines. Part 36. New synthesis of ethyl 1-alkyl-1,4,5,6-tetrahydro-6-oxopyridine-3-carboxylates and 1-alkyl-1,4,5,6-tetranydro-6-oxopyridine-3-carbonitriles through reduction of N-2-nitroarylamidines

Abstract

Ethyl 1-alkyl-1,4-dihydropyridine-3-carboxylates 2a–d and 1-alkyl-1,4-dihydropyridine-3-carbonitriles 2e,f were allowed to react with 2-nitrophenyl azide 3 to give tertiary amidines 4 by spontaneous rearrangement of the triazoline cycloadducts. Ready catalytic hydrogenation with Pd–C of 4 gave the corresponding ethyl 1-alkyl-6-oxo-1,4,5,6-tetrahydropyridine-3-carboxylates 5a–d and 1-alkyl-6-oxo-1,4,5,6-tetrahydropyridine-3-carbonitriles 5e,f.