合成路线1

Acylation of Meldrum's acid (I) with propionyl chloride (II) in the presence of pyridine gave propionyl derivative (III). Subsequent ring opening of (III) with propanethiol (IV), followed by decarboxylation provided S-propyl 3-oxothiovalerate (V). Propyl 3-amino-3-(m-chlorophenyl)-2-propenoate (VII) was prepared by reaction of (3-chlorobenzoyl)acetate (VI) with ammonium acetate in refluxing ethanol. Then, Hantzsch condensation of ketothioester (V), beta-enaminoester (VII), and propionaldehyde (VIII) in EtOH at 80 C in a sealed tube furnished the dihydropyridine (IX). Finally, oxidation of (IX) using chloranil (X) in boiling THF gave the target pyridine.