Ethylene Glycol → Diethyl 2-methyl-4-(2-nitrophenyl)-6-ethylenedioxymethyl-1,4-dihydropyridine-3,5-dicarboxylate

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A mixture of diethyl 2-methyl-4-(2-nitrophenyl)-6-formyl-1,4-dihydropyridine-3,5-dicarboxylate (388.37 mg), ethylene glycol (186.21 mg) and p-toluenesulfonic acid (catalytic amount) in absolute benzene. (5 ml) was refluxed for 45 minutes under azeotropic dehydration. The reaction mixture was allowed to stand and washed twice with an aqueous solution of sodium bicarbonate. After removal of the solvent, the residue immediately turned into crystals. Thus obtained crystals were recrystallized from a mixture of ethanol and diisopropyl ether to give yellow pure crystals (0.32 g) of diethyl 2-methyl-4-(2-nitrophenyl)-6-ethylenedioxymethyl-1,4-dihydropyridine-3,5-dicarboxylate, m.p. 152° to 153.5° C.

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