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 A Synthetic Method of 2,3-Diphenyl-1,3-butadiene
  • A Synthetic Method of 2,3-Diphenyl-1,3-butadiene
  • 2,3-Diphenyl-1,3-Butadiene (CAS no.: 2548-47-2), which is also known as 1,3-Butadiene, 2,3-diphenyl, could be made from the following synthetic routes.

    A 300-ml., three-necked, round-bottomed flask is fitted with a sealed mechanical stirrer, a thermometer, and a reflux condenser to which is attached a T-tube connected to a source of pure nitrogen. The remaining joint of the T-tube is connected to a bubbling device so that the rate of nitrogen flow can be observed throughout the course of the reaction. The flask is flushed with nitrogen and charged with 30 ml. of anhydrous dimethyl sulfoxide and 2.4 g. of about 50% sodium hydride in oil (ca. 0.05 mole). Stirring is begun and the contents of the flask are heated to 75° for 30 minutes under a slight pressure of nitrogen. The flask is cooled in a water bath to 30°, before a solution of 4.45 g. (0.0250 mole) of diphenylacetylene in 20 ml. of anhydrous dimethyl sulfoxide is added dropwise with stirring to the dark-gray solution. During the addition, the temperature of the reaction mixture gradually rises until it approaches 40°. After the addition is completed, the reaction mixture is heated to 65° and held at this temperature for 2.5 hours. The resulting red-brown reaction mixture is cooled to room temperature and poured into 500 ml. of an ice and water mixture with stirring. After the ice has melted, the mixture is extracted with five 150 ml. portions of diethyl ether. The ether extracts are combined, washed with three 100-ml. portions of water, then dried over sodium sulfate. The ether is removed by distillation at reduced pressure, and the product (about 6.0 g.) is chromatographed on 180 g. of alumina. Elution with 1:7 (v/v) benzene:n-hexane gives ten 50-ml. fractions, of which the first two contain nearly all the mineral oil from the sodium hydride reagent. Fractions 3 through 8 are combined, and the ether is removed by distillation, yielding 1.2–1.4 g. (22–25%) of slightly impure 2,3-diphenyl-1,3-butadiene. Recrystallization from methanol gives 0.55–0.70 g. (10.7–13.6%) of pure 2,3-diphenyl-1,3-butadiene, m.p. 47–48°.

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