5-Carboxy-2-Furanpropionic Acid

Abstract

Ethyl 2-[5-(Ethoxycarbonyl)furfuryl]acetoacetate. Freshly cut sodium (10 g, i.e., 0.43 g-atom) was added in small pieces to 150 ml of dry methanol contained in a 500-ml three-necked round-bottomed flask fitted with mercury-sealed stirrer, dropping funnel, and reflux condenser. When the whole of the sodium had dissolved, the solution was allowed to cool to room temperature, and 80 g (0.6 mole) of freshly distilled acetoacetic ester was stirred in rapidly (see Notes). Stirring was continued further for 25–30 minutes, and then, over a period of about 40 minutes, 30 g (0.17 mole) of methyl 5-(chloromethyl)-2-furoate (see Vol. 1 of this work, p. 29), b.p. 114–116°/3 mm, was added slowly from the dropping funnel. With continued stirring the reaction mixture was boiled in a water bath for 2–2.5 hours, after which time the reflux condenser was replaced by one set for distillation and methanol was distilled off completely. When the residue was cool, 100 ml of cold water was added, the oily layer was separated, and the aqueous layer was extracted several times with small portions of ether. The ether extracts were added to the main product, which was then dried over calcined sodium sulfate. Solvent was distilled off, and the residue was vacuum-distilled with collection of the substance coming over at 152–157°/2 mm. The yield of 2-[5-(ethoxycarbonyl)furfuryl]acetoacetic ester, a light-yellow liquid, was 25.5–27.8 g (55.4–60.5%).