Synthesis of some novel 1,2,4-triazolo[4,3-a]2H-pyrano [3,2-e]pyridine derivatives

Substituted 2H-pyrano[3, 2-e][1,2,4]triazolo[4,3-a]pyridine 3a-f and 4a-b have been prepared starting from 5-methyl-6-cyano-7-hydrazino-2-oxo-2H-pyrano[2,3-b] pyridine-3-carboxylic acid 2. The compound 2 is prepared by reacting ethyl-5-methyl-6cyano-7-chloro-2-oxo-2H-pyrano [2,3-b]pyridine-3-carboxylate 1 with hydrazine hydrate at room temperature with good yield. Condensation of 2 with acids results in the formation of 1-substituted 2H-pyrano[3,2-a][1,2,4]triazolo[4,3-a]pyridine (3a-f), further the hydrazine derivative 2 has been transformed to 1-aryl-2H-pyrano[3,2-a][1,2,4]triazolo[4,3-a]pyridine (4a-b). These compounds are expected to have antihypertensive activity.