(E)-1,4-Dibromobut-2-ene

106-99-0

821-06-7

Example 1 (E)-1,4-dibromo-2-butene (A) Synthesis: 1,3-butadiene (60 mL, 0.70 mol) was added to a 500 mL round-bottomed flask and the flask was placed in a -78 °C cooling bath. Carbon tetrachloride (CCl4, 100 mL) pre-cooled to -20 °C was slowly added to the flask to ensure that the temperature of the reaction mixture was maintained below -20 °C. Subsequently, bromine was added dropwise over a period of 2 hours. The reaction mixture was stirred vigorously at room temperature for 14 hours. After completion of the reaction, most of the solvent was evaporated under reduced pressure. The crude product was purified by recrystallization from cold hexane to afford white crystalline 1,4-dibromo-2-butene (A) (62.4 g, 0.29 mmol) in 58% yield. Thin layer chromatography (TLC) showed an Rf value of 0.74 (unfolding agent ratio hexane:ethyl acetate = 4:1). Nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 300.40 MHz, CDCl3) data were as follows: δ 3.89-4.02 (m, 4H), 5.90-6.05 (m, 2H) ppm.