Research on heterocyclic compounds. XLIII. Synthetic studies on 1,4-dihydropyridine derivatives

In order to obtain N‐benzyl‐3,5‐dicarbethoxy‐2,6‐dimethyl‐4‐phenyl‐1,4‐dihydropyridine 1 as a lead compound of pharmacological interest, the classical Hantzsch synthetic method and the modified Collie procedure were used. However, only a very low yield of 1 was obtained in a mixture with larger amounts of some by‐products (2, 3, 4). Compound 1 was then synthesized in satisfactory yield via a different method, together with another by‐product (9). The structures of all by‐products were elucidated and possible mechanisms leading to the formation of such compounds are described.