Imidazolium chloride

Comparative in Analogy to from WO-A-00/14072 In a flask, 68.22 g of imidazole are suspended in 505 g of xylene. The mixture is heated to reflux and dewatered by taking off 5 g of a xylene/water mixture. The temperature is reduced to 66° C. and over the course of 30 minutes 25.2 g of phosgene are metered in with an introduction rate of 50.4 g/h. After about 15 minutes the reaction mixture takes on a consistency like that of chewing gum. When the metering of phosgene is at an end the imidazole hydrochloride by-product is in the form of yellow balls. After a further hour of stirring at this temperature, this temperature is raised to 130° C., and the consistency of the imidazole hydrochloride changes to a brown melt. The melt is drained off at 130° C. It solidifies on cooling to a dark-green, solid mass. The supernatant xylene phase is cooled to 0° C. The precipitated crystals are filtered off and dried at 20 mbar and 50° C. This gives carbonylbisimidazole in the form of white crystals with black fractions (Hazen colour number: 489). The purity is 96.8percent, corresponding to a yield of 70percent of theory.Inventive; A flask is charged with 375.2 g of dry chloroform and 93.8 g of imidazole and this initial charge is heated to 35° C. At this temperature over the course of 1.75 hours 35.02 g of phosgene are added with an introduction rate of 20.0 g/h. The mixture thus obtained is subsequently stirred at the same temperature for 1.5 h. In order to ensure a phosgene-free reaction mixture, 28 g of distillate are taken off under a pressure of 280 mbar and at 30° C., an ammonia/water/isopropanol mixture is added to the distillate, and this mixture is discarded. The imidazole hydrochloride by-product (isolated dry weight: 72.1 g) is removed by filtration at 35° C., the filter cake being washed with twice 100 ml of warm chloroform at 35° C. 251.1 g of water-clear solution are distilled off from the combined organic phases at 280 mbar and 30° C. The remaining solution is cooled to 0° C., and a suspension forms. The precipitated carbonyl bisimidazole is separated off by filtration and additionally washed with 50 ml of chloroform conditioned to a temperature of 0° C. Drying of the crystals at 6 mbar and 30° C. gives 41.5 g of product in the form of white crystals having a Hazen colour number of 44. The purity of the product is 99.5percent, corresponding to a yield of 74.0percent of theory.; Inventive; A flask is charged with 358.1 g of dry chloroform and 119.36 g of imidazole and this initial charge is heated to 55° C. At this temperature over the course of 1.75 hours 44.57 g of phosgene are added with an introduction rate of 25.5 g/h. The mixture thus obtained is subsequently stirred at the same temperature for 2 h. In order to ensure a phosgene-free reaction mixture, 5.4 g of distillate are taken off under a pressure of 630 mbar and at 35° C., an ammonia/water/isopropanol mixture is added to the distillate, and this mixture is discarded. The imidazole hydrochloride by-product (isolated dry weight: 96.0 g) is removed by filtration at 55° C., the filter cake being washed with twice 100 ml of warm chloroform at 55° C. The combined organic phases are cooled to 0° C., and a suspension forms. The precipitated carbonyl bisimidazole is separated off by filtration and additionally washed with 50 ml of chloroform conditioned to a temperature of 0° C. Drying of the residue at 4 mbar and 46° C. gives 44.3 g of product in crystalline form having a Hazen colour number of 49. The purity of the product is 99.0percent, corresponding to a yield of 61.9percent of theory.Inventive; A flask is charged with 531.5 g of dry dichloromethane and 93.8 g (1.37 mol) of imidazole and this initial charge is heated to 35° C. At this temperature over the course of 1.75 hours 36.04 g (0.36 mol) of phosgene are added with an introduction rate of 20.6 g/h. The mixture thus obtained is subsequently stirred at the same temperature for 1.5 h. In order to ensure a phosgene-free reaction mixture, 13.2 g of distillate are taken off under a pressure of 790 to 500 mbar and at 35-25° C., an ammonia/water/isopropanol mixture is added to the distillate, and this mixture is discarded. The imidazole hydrochloride by-product (isolated dry weight: 72.1 g) is removed by filtration at 35° C., the filter cake being washed with twice 100 ml of warm dichloromethane at 33° C. 250.1 g of water-clear solution are distilled off from the combined organic phases at 790 to 500 mbar and 35-25° C. The remaining solution is cooled to 0° C., and a suspension forms. The precipitated carbonyl bisimidazole is separated off by filtration and additionally washed with 50 ml of dichloromethane conditioned to a temperature of 0° C. Drying of the crystals at 4 mbar and 30° C. gives 40.0 g of product in the form of white crystals, Hazen colour number: 69.7. The purity of the product is 99.3percent, corresponding to a yield of 71.2percent of theory.; Example 5 Inventive with Recycling of the Mother Liquor 1st Phosgenation A flask is charged with 531.5 g of dry dichloromethane and 93.8 g (1.37 mol) of imidazole and this initial charge is heated to 35° C. At this temperature over the course of 1.75 hours 35.02 g (0.35 mol) of phosgene are added with an introduction rate of 20.0 g/h. The mixture thus obtained is subsequently stirred at the same temperature for 1.5 h. In order to ensure a phosgene-free reaction mixture, 8.4 g of distillate are taken off under a pressure of 750 to 500 mbar and at 35-20° C., an ammonia/water/isopropanol mixture is added to the distillate, and this mixture is discarded. The imidazole hydrochloride by-product (isolated dry weight: 80.3 g) is removed by filtration at 35° C., the filter cake being washed with twice 100 ml of warm dichloromethane at 33° C. The remaining solution is cooled to 0° C., and a suspension forms. The precipitated carbonyl bisimidazole is separated off by filtration and additionally washed with 50 ml of dichloromethane conditioned to a temperature of 0° C. After the solid carbonylbisimidazole has been filtered off, 553.0 g of mother liquor M1 are obtained. Drying of the crystals at 5 mbar and 20° C. gives 33.54 g of product in the form of white crystals with a Hazen colour number of 45.1. The purity of the product is 99.6percent. The yield therefore corresponds to 59.9percent of theory. 2nd Phosgenation A flask is charged with 531.5 g of dichloromethane-containing mother liquor M1 from the 1st phosgenation step and 93.8 g (1.37 mol) of imidazole and this initial charge is heated to 35° C. At this temperature over the course of 1.75 hours 35.02 g (0.35 mol) of phosgene are added with an introduction rate of 20.0 g/h. The mixture thus obtained is subsequently stirred at the same temperature for 1.5 h. In order to ensure a phosgene-free reaction mixture, 21.6 g of distillate are taken off under a pressure of 750 to 450 mbar and at 35-20° C., an ammonia/water/isopropanol mixture is added to the distillate, and this mixture is discarded. The imidazole hydrochloride by-product (isolated dry weight: 86.6 g) is removed by filtration at 35° C., the filter cake being washed with twice 100 ml of warm dichloromethane at 33° C. The remaining solution is cooled to 0° C., and a suspension forms. The precipitated carbonyl bisimidazole is separated off by filtration and additionally washed with 100 ml of dichloromethane conditioned to a temperature of 0° C. After the solid carbonylbisimidazole has been filtered off, 553.0 g of mother liquor M2 are obtained. Drying of the crystals at 6 mbar and 30° C. gives 39.4 g of product in the form of white crystals with a Hazen colour number of 33.2. The purity of the product is 98.7percent. The yield therefore corresponds to 70percent of theory. 3rd Phosgenation A flask is charged with 531.5 g of dichloromethane-containing mother liquor M2 from the 2nd phosgenation step and 93.8 g (1.37 mol) of imidazole and this initial charge is heated to 35° C. At this temperature over the course of 1.75 hours 35.02 g (0.35 mol) of phosgene are added with an introduction rate of 20.0 g/h. The mixture thus obtained is subsequently stirred at the same temperature for 1.5 h. In order to ensure a phosgene-free reaction mixture, 9.2 g of distillate are taken off under a pressure of 750 to 500 mbar and at 35-20° C., an ammonia/water/isopropanol mixture is added to the distillate, and this mixture is discarded. The imidazole hydrochloride by-product (isolated dry weight: 88.1 g) is removed by filtration at 35° C., the filter cake being washed with twice 100 ml of warm dichloromethane at 33° C. The remaining solution is cooled to 0° C., and a suspension forms. The precipitated carbonyl bisimidazole is separated off by filtration and additionally washed with 100 ml of dichloromethane conditioned to a temperature of 0° C. Drying of the crystals at 7 mbar and 20° C. gives 37.3 g of product in the form of white crystals with a Hazen colour number of 41.0. The purity of the product is 98.5percent. The yield therefore corresponds to 65.9percent of theory.To a 1000 ml flask were added 108.3 g (1.59 mol) of imidazole and 630 g of tetrahydrofuran. After the atmosphere of the system was replaced with nitrogen, the imidazole was dissolved under stirring. Thereto was added dropwise 39.3 g (0.2 mol) of diphosgene at room temperature over a period of 2 hours. After completion of the dropwise addition, the stirring was continued at room temperature for 1 hour and then the whole was heated to 55°C, followed by continuous stirring for another 1 hour. Imidazole hydrochloride yielded as a by-product was filtrated with heat and was then washed with 100 g of tetrahydrofuran. The imidazole hydrochloride filtrated off was dried under reduced pressure at 40°C to obtain 83.2 g (0.796 mol) of imidazole hydrochloride (recovery of 100percent). A filtrate containing CDI was concentrated and subjected to toluene-crystallization, and CDI was filtrated off under a nitrogen atmosphere. The CDI filtrated off was dried under reduced pressure at 40°C to obtain 58.0 g (0.358 mol) of CDI as white crystals (yield 90percent). M.p. 111.2 to 118.6°C.