Patent ID: 7329756

Claim:
An improved method for the manufacture of 4-(4-Benzofuranzanyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylic acid methyl 1-methylethyl ester comprising the steps of: (i) reacting 2,1,3-benzoxadiazole-4-carboxaldehyde with methyl acetoacetate in the presence of acetic acid and piperidine in diisopropyl ether to obtain 2-acetyl-3-benzofurazan-4-yl-acrylic acid methyl ester; (ii) isolating and purifying 2-acetyl-3-benzofuran-4-yl-acrylic acid methyl ester to obtain purified 2-acetyl-3-benzofuran-4-yl-acrylic acid methyl ester by recrystallizaton from a solvent; (iii) reacting 2-acetyl-3-benzofuran-4-yl-acrylic acid methyl ester with isopropyl-β-aminoacrotonate in ethanol to obtain 4-(4-Benzofuranzanyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylic acid methyl 1-methylethyl ester.