hantzsch 1 ,4- dihy&opyridines; are rapidly oxidized to the corresponding pyridine derivatives using zinc chlorochromate nonahydrate [zn(c1cro ) .9h o] in dichloromethane at room temperature. in addition to aromatization, no loss of the 4- substituent is observed

ABSTRACT FeNH4(SO4)2·12H2O (alum) efficiently catalyzes the one-pot three-component reaction of dimedone, aldehydes, and 3-aminocrotonate to afford 1,4-dihydropyridines. The work-up is easy, and the products are obtained in good to excellent yields and high purity. GRAPHICAL ABSTRACT

Domestic microwave ovens as well as laboratory reactors have been successfully employed to prepare dialkyl 1,4-dihydropyridine-3,5-dicarboxylates and to induce the synthesis of the corresponding aromatic derivatives. In that latter particular case, unexpected results have been reported.