5-Methylfurfural → 3-(Ethoxycarbonyl)-4-(5-methyl-2-furyl)but-3-enoic Acid

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Reaction Steps

Sodium ethylate (74.2 g, 1.09 mol) was added under vigorous stirring to a solution of 5-methyl-2-furaldehyde 1 (100 g, 0.91 mol) and diethyl succinate (316 g, 1.81 mol) in ethanol (1 L). The reaction mixture was refluxed for 8 h and evaporated in vacuum (˜20 mmHg) at 50° C. until the solvent distillation ceased. The obtained residue was diluted with 500 mL of 10% HCl and 500 mL of ethyl acetate. The mixture was shaken. The organic layer was separated, diluted with 500 mL of a saturated aqueous solution of NaHCO3, and shaken. The aqueous layer was separated, acidified with 10% HCl to pH 2, and subjected to extraction with 1 L of ethyl acetate. The organic layer was evaporated in vacuum (˜20 mmHg) at 60° C. and chromatographed on a layer of silica gel (200×150 mm) with hexane/ethyl acetate mixture, 1:1 as eluent. Fractions with the target product were collected and evaporated in vacuum to give 45 g (0.19 mol, 21%) of the desired compound as a yellow solid.

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