A mixture of 96 g (1 mole) of freshly distilled 2-furaldehyde, b.p. 154–155°/680 mm, 160 g (1 mole) of diethyl malonate, and 153 g (1.5 moles) of acetic anhydride was prepared in a 750-ml round-bottomed flask fitted with a reflux condenser protected by a calcium chloride tube. The mixture was heated in a bath of Wood’s metal at a bath temperature of 175–180° for six hours. The reaction mixture was cooled, 200 ml of water was added, and the dark oil that separated was transferred to a one-liter beaker and stirred with a glass rod while saturated sodium carbonate solution was added until the reaction was weakly alkaline. Ether (100 ml) was added to the mixture, the upper layer was separated, and the aqueous layer was extracted with four 100-ml portions of ether. The combined ether extract was washed with water and dried with anhydrous sodium sulfate. Solvent was distilled off, and the residue was vacuum-fractionated from a flask having a small Vigreux column. A head fraction, consisting essentially of unchanged malonic ester (see Notes), was collected up to 147°/2 mm, and diethyl furfurylidenemalonate came over at 147–148°/2 mm as a light-yellow liquid.
KeywordsAcetic Anhydride Heterocyclic Compound Anhydrous Sodium Sulfate Bath Temperature Reflux Condenser
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