Synthesis of 2,6-Dimethyl-5carbethoxy-3-substituted pyridines of pharmaceutical interest

ABSTRACT

Condensation of 2,6-dimethyl-3,5-dicarbethoxypyridine [I] with hydrazine hydrate in different solvents [reaction media] afforded a mixture of 5-carbethoxy-2,6-dimethyl- pyridine-3-carboxyhydrazide [IIa] and 2,6-dimethylpyridine-3,5-bis [carboxyhydrazide] [IIb] in a ratio depending on the reaction time and the solvent polarity. Reaction of [IIa] with different aldehydes gave the corresponding arylidenehydrazides [III] which on reacting with acetic anhydride afforded the respective oxadiazolines [IV]. The 5-carbethoxylutidine- 3-carboxsemicarbazides [V] and the 3-carbox-thiosemicarbazides [VI] were obtained via condensation of [IIa] with some isocyanates and isothiocyanates, respectively