DE1179210B - Process for the preparation of N-vinylimidazoles - Google Patents

Description

Process for the preparation of N-vinylimidazoles It is known that one N-vinylimidazole from N-oxyethylimidazole when passing over dehydrating Receives catalysts. N-vinylimidazoles can also be removed by the action of acetylene to imidazoles in the presence of alkaline substances, alkali zincates or zinc or cadmium salts of organic acids obtained at elevated temperature, whereby the rate of reaction by adding tertiary organic nitrogen bases can increase.

It is already known that N-vinylimidazoles can be reacted the corresponding imidazole potassium compounds can produce with acetylene. the The imidazole potassium compounds used as starting materials can be prepared but only with the help of a great deal of technical effort and under considerable safety precautions carry out.

Other disadvantages of this method are that in the Reaction forms undesirable by-products and that the potassium in the implementation can practically not be returned to the process on an industrial scale.

If you use the corresponding imidazole potassium compounds as a catalyst if used, good yields are obtained in some cases. On the other hand, if you vinyl imidazoles in In the presence of the other catalysts mentioned, only low yields are achieved Obtained N-vinylimidazoles.

It has now been found that you can N-vinylimidazoles by reacting Imidazoles with acetylene at elevated temperatures and elevated pressures in the presence of catalysts can be prepared in an advantageous manner if you can do the reaction in the presence of 0.1 to 5 percent by weight copper acetylide, based on the applied Imidazoles, or of salts which form copper acetylide under the reaction conditions performs. This was surprising, since the action of acetylene on cyclic Amines, such as pyrrolidine or piperidine, which still have a hydrogen atom on the ring nitrogen wear, at elevated temperatures and pressures in the presence of copper acetylide the corresponding n-butyne compounds are formed as a catalyst.

In addition to the unsubstituted imidazole, substituted ones can also be used Vinylate imidazoles that still have a hydrogen atom on one nitrogen atom.

Vinylable imidazoles are z. B. benzimidazole, 4,5-dimethylimidazole, 4-methyl-5-phenylimidazole, 2-methylimidazole, 2,4,5-trimethylimidazole, 4-methyl-5-benzylimidazole, 2-phenylbenzimidazole, 4-methylbenzimidazole.

The acetylene is expediently carried out in a mixture with among the Inert reaction conditions Gases of implementation too. As an inert gas, for. B. Use nitrogen. The partial pressure of the acetylene in the gas mixture can be within further limits can be varied. In this way, gas mixtures can be used where the partial pressure of the acetylene is between 1 and 60 atm.

The copper acetylide and the copper salts used as catalysts can optionally be on porous supports made of aluminum oxide or silicon oxide applied and fixed in the reaction vessel. Under the reaction conditions the copper salt is converted into copper acetylide.

Copper (I) chloride, bromide, iodide, oxide, Use copper (II) sulfate or carbonate.

The process can be carried out continuously or discontinuously. One works in general at a pressure of 10 to 250 at, preferably from 50 to 80 at, and a temperature of 80 to 280 "C, preferably 100 to 180" C. You can work with or without a solvent. The solvent can be, for. B. tetrahydrofuran, dioxane or the imidazole to be vinylated corresponding Use N-vinylimidazole. The N-vinylimidazoles are e.g. B. valuable monomers for the manufacture of polymers.

The parts mentioned in the examples are parts by weight. Parts by weight relate to parts of space as grams to liters.

Example 1 From a vertical, high-pressure-resistant pipe Stainless steel of 2 parts of the volume is 1500 parts of an hour from below Pumped solution of the following composition: 1046 parts of tetrahydrofuran, 448 parts Imidazole, 6 parts dicopper chloride. At the same time, a gas mixture is generated below 60 at existing of 50 percent by volume nitrogen and 50 percent by volume acetylene, passed through the pipe. The reaction temperature is adjusted to 160 to 1700C by electrical heating. Every hour, 300 parts by volume of gas, which is about 25 percent by volume acetylene and nitrogen contains, relaxed. The reaction mixture obtained over the course of one hour becomes first by distillation in vacuo at 20 Torr and 40 "C the solvent removed. In the further course of the distillation at 75 to 82 "C and 11 Torr 425 parts of N-vinylimidazole were obtained.

The fraction from 120 to 142 "C at 0.4 Torr consists of 113 parts unreacted imidazole. 36 parts of viscous, dark material remain in the residue Product. The conversion is 68 ° lo, the yield 92% of theory, based on the converted Imidazole.

Example 2 In a vertical, high-pressure-resistant pipe Stainless steel of 2 volume parts are 1.4 volume parts of a catalytic converter, which consists of 120 / o copper oxide on silicon oxide, firmly arranged.

The Cu2 + salt contained in the catalyst is pumped in for several hours from 70/0 aqueous formaldehyde solution at 70 "C under nitrogen to Cu9, + - salt reduced. The Cu + salt is then pressed in by injecting an acetylene-nitrogen mixture converted into copper acetylide in a ratio of 1: 1 at 30 atm.

Thereupon 1000 parts per hour are released through the pipe from below pumped in a solution containing 700 parts of tetrahydrofuran and 300 parts of imidazole. At the same time, a gas mixture consisting of 50 percent by volume of nitrogen is generated under 60 atm and 50 percent by volume acetylene is passed through the tube.

The reaction temperature is raised to 150 bis by electrical heating 1600C set. Every hour, 220 parts of the volume of gas, which is around 25 percent by volume Contains acetylene, relaxed.

The reaction mixture is worked up as in Example 1 described. After removal of the solvent, Kr 0.4 is obtained 46 to 52 "C 254 parts N-vinylimidazole and at Kr.04 118 to 144" C 98 parts not converted imidazole. 28 parts remain as residue. The conversion is 61%, the yield 91 0 / o of theory, based on converted imidazole.

Example 3 From a vertical, high-pressure-resistant pipe Stainless steel of 2 parts of the volume are converted from below every hour 1295 parts of a Solution of the following composition-pumped: 890 parts of tetrahydrofuran, 400 parts of benzimidazole, 5 parts of dicopper dichloride. At the same time, a gas mixture is created below 60 atm of 50 percent by volume nitrogen and 50 percent by volume acetylene, passed through the pipe. The reaction temperature is adjusted to 130 to 150 ° C. by electrical heating. Every hour, 300 parts by volume of gas, which is about 25 percent by volume acetylene and nitrogen contains, relaxed.

The reaction mixture obtained in the course of one hour first becomes the solvent is removed by distillation in vacuo at 20 torr and 40 "C. Im Further distillation is at 148 to 154 "C and 12 Torr 411 parts Obtained N-vinylbenzimidazole. 57 parts of viscous, dark material remain in the residue Product. The conversion of benzimidazole to N-vinylbenzimidazole is 840 /, the theory.

Claims (2)

Claims: 1. Process for the preparation of N-vinylimidazoles by reacting imidazoles with acetylene at elevated temperatures and elevated temperatures Pressures in the presence of catalysts, d a characterized in that the reaction in the presence of 0.1 to 5 percent by weight copper acetylide, based on the applied Imidazoles, or copper salts which form copper acetylide under the reaction conditions performs. 2. The method according to claim 1, characterized in that the copper acetylide or the copper salts are deposited on a porous support made of aluminum or silicon oxide are. Documents considered: German Patent No. 708 262; Justus Liebig's Annalen der Chemie, Vol. 601 (1956), pp. 128 to 134.