反应详情

20 g (0.105 mole) of triethyloxonium-tetrafluoroborate is dissolved in 200 ml of methylene chloride. To the solution is added 18.8 g (0.1 mole) of crystalline 2-(2-imidazolidinylidene)-acetophenone [m.p. 211°-212°, see J. Klosa, Arch.Pharmaz. 286, 397 (1953)]. After the slightly exothermic reaction has subsided, the reaction mixture, a clear yellow solution, is stirred for 16 hours at room temperature; it is subsequently concentrated to dryness in the rotary evaporator; and the crystallising residue is suspended in 300 ml of ethyl acetate. The suspension is cooled to 5°, and the crystals are filtered off with suction to obtain 2-(2-ethoxy-2-phenyl-ethenyl)-2-imidazoline-tetrafluoroborate, m.p. 151°-152°. After drying at 60° in vacuo, the product is further employed without additional purification.

1. customAfter the slightly exothermic reaction
2. concentrationit is subsequently concentrated to dryness in the rotary evaporator
3. temperatureThe suspension is cooled to 5°
4. filtrationthe crystals are filtered off with suction