Citric Acid → 1-tert-Butyl 3-methyl 2,3-dihydropyridine-1,3(6H)-dicarboxylate

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Reaction Steps

1,1'-Carbonyldiimidazole (4 g, 24.7 mmol) in methylene chloride (100 ml) was added dropwise to a solution of 1-tert-butoxycarbonyl-1,2,3,6-tetrahydropyridine-3-carboxylic acid (5 g, 22 mmol) in methylene chloride (200 ml) under a nitrogen atmosphere. Stirring was continued for 1 h followed by addition of methanol (300 ml), and reflux for 26 h. 10% aqueous citric acid (100 ml) was added and the mixture extracted with methylene chloride. The organic layer was dried over magnesium sulphate, evaporated to dryness in vacuo and purified on a silica gel column (Eluent: methylene chloride/methanol (90/1)) to give methyl 1-tert-butoxycarbonyl-1,2,3,6-tetrahydropyridine-3-carboxylate as yellow oil. (Yield: 3.9 g, 73%)

Provenance & Evidence