p-Toluenesulfonic acid → Ethyl 2-methyl-4-(2-thienyl)-5-oxo-1,4,5,7-tetrahydrofuro[3,4-b]pyridine-3-carboxylate

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Reaction Steps

A solution of diethyl 2-methyl-4-(2-thienyl)-6-hydroxymethyl-1,4-dihydropyridine-3,5-dicarboxylate (400 mg) and p-toluenesulfonic acid (catalytic amount) in 99% ethanol (10 ml) was refluxed with stirring for 2 hours. After the resultant solution was concentrated, the residue was pulverized. The powder was recrystallized from ethyl acetate to give colorless prisms (203.2 mg) of ethyl 2-methyl-4-(2-thienyl)-5-oxo-1,4,5,7-tetrahydrofuro[3,4-b]pyridine-3-carboxylate, m.p. 232° C.

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