DE2733466A1 - Imidazole derivs. prodn. - by reacting 1,2-di:amine with carboxylic acid or dehydrogenating imidazoline in presence of zinc oxide - Google Patents

Abstract

Prodn. of imidazoles of formula (I) comprises (a) reacting 1,2-diamines of formula (II) with carboxylic acids of formula (III) or (b) dehydrogenating 2-imidazolines of formula (IV), in either case by heating at 300-600 degrees C in the presence of zinc oxide or a mixt. of zinc oxide and aluminium oxide as catalyst: (R1 - R4 = H or an aliphatic, araliphatic, cycloaliphatic or aromatic residue). (I) are intermediates for dyes, plant protection agents, textile aids, polyurethane and epoxy resin catalysts, surfactants and pharmaceuticals (e.g. nitroimidazoles). They can also be used as catalysts for polymerisations and aldol condensations. (I) is obtd. in good yields and purity. The catalysts used are cheap and easily regenerated, and are not significantly poisoned after prolonged use.

Description

Process for the preparation of imidazoles

Addition to patent applications P 27 29 017.1 and P 27 28 976.5 The invention relates to a new process for the preparation of imidazoles by reacting l-substituted 2-imidazolines at temperatures from 300 to 6000C in the presence of zinc oxide or a mixture of zinc oxide and aluminum oxide as catalysts.

It is known from German Offenlegungsschrift 1 952 991 that one alkylenediamines with carbonyl compounds in the presence of a copper and / or Chromium catalyst can convert to imidazoles at 320 to 6500C. Like all examples show, additional hydrogen must be added to the reaction; recyclable By-products are not obtained.

U.S. Patent 2,847,417 describes the preparation of imidazoles from alkylenediamines and carboxylic acids on supported platinum metal catalysts. Such Catalysts are expensive and are made by certain substances like sulfur, heavy metals or halides easily poisoned. Noble metal catalysts require complex manufacturing processes, to ensure the uniform effectiveness of the catalyst, as well as very pure Starting materials so as not to impair the effectiveness of the catalyst. Like description (Column 1, lines 50 to 70, Column 2, lines 65 to 70) and the examples show In this process, too, hydrogen is added to promote the formation Avoid tarry polymers and deposits on the catalyst and increase the effectiveness of the catalyst as long as possible.

It is known from Russian patent specification 201 418 that 2-methylimidazoline in the presence of a metal catalyst and with diphenyl oxide as the reaction medium dehydrogenated to 2-methylimidazole at a temperature of 180 to 2300C. The patent specification shows in one example that amounts of 47 grams of starting material are converted. If you carry out the implementation in the liquid phase on an industrial scale Measures by, you get a much lower yield up to less than 60 % of theory. A significant proportion of imidazole is formed by dealkylation, and more so, the higher the conversion to 2-methylimidazole. The procedure is therefore in terms of saving expensive solvents, good yield and simple and economic operation unsatisfactory. On the other hand, there would be a high turnover Worth striving for, because so the separation of the unreacted imidazoline by distillation is no longer required.

Such an advantage would be particularly in the case of the manufacture of high melting points Imidazoles, e.g. of 1,2-diphenylimidazole, are of importance.

The subject of patent applications P 27 29 017.1 and P 27 28 976.5 is a process for the preparation of imidazoles of the formula where R1, R2 and R5 can be identical or different and each represent an aliphatic, araliphatic or aromatic radical or a hydrogen atom, by reaction of 2-imidazolines of the formula wherein R1, R2 and R5 have the aforementioned meaning at a temperature of 300 to 60o0c in the presence of zinc oxide or a mixture of zinc oxide and aluminum oxide as catalysts.

vrvn -It has now been found that the process of these patent applications results in a process for the preparation of imidazoles of the formula in which R1, R2, R3 and R4 can be identical or different and each denote an aliphatic, cycloaliphatic, araliphatic or aromatic radical, R1, R2, R3 can also denote a hydrogen atom, can be further developed if, instead of the starting materials III 2 -Imidazolines of the formula in which R1, R2, R3 and R4 are as defined above.

In the case of using 1,2-diphenylimidazoline, the reaction can be represented by the following formulas: Compared to the known processes, the process according to the invention provides imidazoles in a simpler and more economical way in good yield and purity. Although no additional hydrogen is added, formation of tarry polymers, deposits on the catalyst and a rapid decrease in catalyst activity are not observed. The addition of hydrogen is neither necessary nor expedient. Compared to the catalysts of the known processes, the catalysts according to the invention are cheaper, easier to regenerate and are not poisoned to a significant extent during a prolonged period of operation. Especially on an industrial scale, the overall result in terms of conversion and yield is better compared to the prior art. All of these advantageous properties are surprising in view of the prior art.

Preferred starting materials IV and correspondingly preferred end materials I are those in whose formulas R1, R2, R3 and R4 can be identical or different and in each case an alkyl radical with 1 to 18 carbon atoms, in particular with 1 to 8 carbon atoms, an alkenyl radical with several double bonds or in particular a double bond and with 2 to 18, preferably 3 to 18, in particular 4 to 8 carbon atoms, a cycloalkyl radical with 5 to 7 carbon atoms, an aralkyl radical with 7 to 12 carbon atoms or a phenyl radical, R1, R2, R3 above also mean a hydrogen atom.

The abovementioned radicals can still be carried out under the reaction conditions inert groups, e.g. alkyl groups or alkoxy groups with 1 to 4 carbon atoms each, be substituted.

The starting materials IV are, for example, in the 2-position, 4-position or 5-position single or in 2 of these positions the same or different twice or in these 3 positions the same or differently three times the methyl, ethyl, allyl, crotyl, propyl, isopropyl, butyl, isobutyl, pentyl, sec-butyl, tert. -Butyl-, hexyl-, heptyl-, octyl-, oleyl-, n-undecen- (ll) -yl- (l) -, Nonyl, decyl, octadecyl, benzyl, cyclohexyl, cyclopentyl, toluyl, xylyl, Naphthyl, methoxyphenyl, ethoxyphenyl, ethylphenyl, dimethoxyphenyl, phenyl group substituted l-phenyl-2-imidazoline, unsubstituted l-phenyl-2-imidazoline; homologous, in the l-position by the methyl, ethyl, allyl, crotyl, propyl, isopropyl, butyl, Isobutyl, Pentyl, sec-butyl, tert-butyl, hexyl, heptyl, Octyl-, oleyl-, n-undecen- (ll) -yl- (l) -, nonyl-, decyl-, octadecyl-, cyclohexyl-, Cyclopentyl, benzyl, toluyl, xylyl, naphthyl, methoxyphenyl, athoxyphenyl, Ethylphenyl, dimethoxyphenyl group substituted 2-imidazolines.

The reaction is expedient at a temperature of from 300 to 6000.degree. C. from 350 to 500 ° C., preferably from 400 to 480 ° C., without pressure or under pressure, expedient from 1 to 50 bar, carried out continuously or batchwise. Usually the reaction mixture also serves as a solution medium; The reaction conditions are inert, organic, expediently no azeotrope with water forming solvents, e.g. aliphatic hydrocarbons such as petroleum ether or Ligroin, can be used. Among the organic solvents 0 are those with a boiling point above 120 C, expediently above 1400 C, e.g. corresponding gasoline fractions from 120 to 1600c, preferred.

The catalyst used is zinc oxide alone or a mixture of zinc oxide and aluminum oxide, suitably in a ratio of zinc to aluminum such as 1 to 50, preferably 8 to 10 gram atom of zinc per gram atom of aluminum, and from 0.1 to 1, preferably from 0.2 to 0.4 gram atom of zinc per mole of starting material IV is used.

A- and t-aluminum oxides, for example, can be used as aluminum oxide.

One can also use zinc compounds under the reaction conditions Zinc oxide, use e.g. one impregnated with zinc chloride or zinc sulphate Alumina. Instead of aluminum oxide, those containing this oxide are also used Substances or mixtures of substances into consideration, e.g. aluminum silicate, magnesium aluminum silicate hydrate, Dimagnesium aluminum silicate hydrate, sodium aluminum silicate, calcium aluminum silicate, Fuller's earth, clays, bleaching earths such as bentonite, bauxite, pumice stone, andalusite, kaolin, Allophanes, zeolites, mullite, corundum, y-alumina, hydrargillite, boehmite.

The catalyst can be unsupported or, advantageously, on a support in an amount of 1 to 18 percent by weight of catalyst, based on the support, be upset. Also can the aforesaid aluminum compounds at the same time in the form of the A1203 contained therein as a catalyst component and serve as a carrier for the zinc oxide. Silica compounds are expediently suitable as carriers such as silicates, e.g., montmorillonite, Florida earth, quartz, asbestos; precipitated silica, Silica gel, kieselguhr; Titanium dioxide, zirconium dioxide, tin dioxide, activated carbon; Alkaline earth sulphate or alkaline earth phosphate, e.g. the calcium or barium salts; or corresponding mixtures the aforementioned carrier materials. The production of the supported catalysts is according to the usual procedures, e.g. by applying the zinc compound and, if necessary the aluminum compound on the support, drying and calcining, for example between 400 and 1200C in a reducing, oxidizing or inert atmosphere, carried out. The carrier can also be in its desired geometric shape a solution of the zinc compound alone or the zinc and aluminum compound, e.g. an aqueous solution of zinc sulfate and optionally aluminum sulfate, soaked and dried. You can also use the carrier material with the zinc compound and optionally knead the aluminum compound and water into the desired Shape, dry and calcine at a temperature of 400 to 1200C.

The particle size of the catalysts is preferably 0.05 to 7, in particular from 2 to 4 millimeters. The shape can be arbitrary, e.g. in pill, Cylindrical or strand shape, spherical or granular, can be selected. Are preferred pore volumes of 0.05 to 1 milliliter per gram for the supported catalyst, specific surface areas from 1 to 300 square meters per gram and bulk weights of 0.4 to 2.1 grams per milliliter.

Catalyst-coated tubes or reticulated supports can also be used use.

The catalysts are preferably used alone or on the support in Split or spherical form used in the fluidized bed, with appropriate catalyst particles with grain sizes from 0.005 to 3 mm, in particular from 0.1 to 1 mm, preferably 0.2 up to 0.4 mm. The height of the catalyst bed in the Vortex condition is advantageously 30 to 2,000, in particular 60 to 80 millimeters, or is expedient chosen so that there are residence times of the starting materials II in the catalyst layer from 0.01 to 20, preferably from 5 to 10 seconds.

With regard to the manufacture of the catalysts, reference is made to Houben-Weyl, Methods of Organic Chemistry, Volume 4/2, pages 142 ff and Ullmanns Encyklopadie der technical chemistry, Volume 9, pages 271 ff, referenced.

The reaction can be carried out as follows: The liquid or vaporous starting material IV, expediently mixed with inert gases, e.g. nitrogen, are at the reaction temperature over the catalyst or catalyst on the Carrier passed in a fixed bed. The reaction mixture emerging in vapor form from the reactor is then dedusted if necessary in a cyclone and in a cooled receiver condensed. The end product is expediently separated off by fractional distillation.

The end product can also be obtained by recrystallization or reprecipitation suitable solvents, e.g. with toluene, dimethylformamide or dilute acids, e.g. with formic acid.

In a preferred embodiment of the process, the starting materials implemented in a fluidized bed at the reaction temperature. The catalyst or Supported catalyst can advantageously be carried out by inert gas or a mixture of starting material IV and inert gas as fluidized bed gas at normal pressure or reduced or increased Pressure can be kept in a fluidized bed. The total amount can be accordingly or a partial amount of starting material IV separately from the fluidized bed gas in the Fluidized bed reactor are initiated. Starting material IV can also be heated in a Storage vessel kept liquid and in an evaporator, the fluidized bed reactor is upstream, be dosed. At the same time it is advantageous to lead a weak one Nitrogen flow, expediently from 5,000 to 50,000 parts by volume of nitrogen per hour, through the evaporator. The vaporized starting material IV is together with the nitrogen flow passed through the catalyst bed. Hydrogen is in all In these cases it can be used as an inert gas, but it is more expedient, if only for reasons of economy and safety, nitrogen is used. The concentration of the Starting material IV in the inert gas is advantageously 0.1 to 50 percent by volume.

One can use the method according to the invention in a simple or subdivided, open or closed fluidized bed system with and without flow dust circulation carry out. With regard to reactors, implementation, process variants and reaction conditions the fluidized bed process is referred to in Ullmann's Encyclopedia of Industrial Chemistry, Volume 1, pages 916 ff. The reaction mixture is worked up in the aforementioned way.

The imidazoles I which can be prepared by the process of the invention are valuable raw materials for the production of dyes, pesticides, Textile auxiliaries, catalysts for polyurethanes and epoxy resins, surface-active Agents and pharmaceuticals, e.g. the corresponding nitroimidazoles. Imidazoles I. are used as catalysts for polymerization reactions and aldol condensations. With regard to the use, reference is made to the aforementioned publications and Ullmanns Encyclopedia of Industrial Chemistry, Volume 8, page 499, referenced.

The parts listed in the following examples are parts by weight. The parts by weight relate to the parts by volume like the kilogram to the liter.

Example 1 100 parts per hour are made from a heated metering device melted l-phenylimidazoline in a horizontal quartz evaporator heated to 3000C dosed. The vapors, along with 5,000 parts by volume of N2 per hour, are passed through a passed to 4000C heated fluidized bed reactor. The vortex reactor is a vertical one on top of the evaporator, electrically heated quartz tube that goes down with a fused quartz frit is complete. The quartz tube is with 200 Parts of a catalyst composed of 90 percent by weight zinc oxide and 10 percent by weight Alumina (Grain size 0.1 to 0.3 mm) half filled.

The residence time in the fluidized catalyst zone is 3.5 Seconds. The height of the catalyst zone in the fluidized state is 80 mm. The the reactor leaving vapors are condensed and fractionally distilled. You get 69.5 parts hourly (76% of theory, based on converted starting material IV) l-Phenylimidazole from bp (2 mbar) 110 to 1120C in addition to 7.3 parts of unreacted 1-phenylimidazoline with a melting point of 45 ° C. The conversion is 92.7 percent, based on converted Starting material IV. The yield remains constant even after 72 hours of operation.

Example 2 100 parts of 1,2-diphenylimidazoline and 50,000 parts by volume Nitrogen are passed every hour through the fluidized bed reactor heated to 5500C. As in Example 1, 65 parts per hour are obtained (71.8% of theory, based on converted starting material IV) 1,2-diphenylimidazole of melting point 90 ° C .; the conversion is 91.3 percent, based on the starting material IV used.

The yield remains constant even after 72 hours of operation.

Example 3 100 parts of 1-phenyl-2-p-tolyl-imidazoline and 50,000 parts by volume The fluidized bed reactor heated to 3500 ° C. is displaced every hour directed. Analogously to Example 1, 70.6 parts per hour (81.3% of theory, based on converted starting material IV) l-phenyl-2-p-tolylimidazole of melting point 1190C. The Y conversion is 87.6%, based on the starting material IV used.

The yield remains constant even after 72 hours of operation.

Example 4 100 parts of 1-phenyl-2- (3 ', 4'-dimethylphenyl) imidazole and 50,000 parts by volume of nitrogen are heated hourly through the heated to 0 400 C. Fluidized bed reactor passed. As in Example 1, 66 parts (77.5 % of theory, based on reacted starting material IV) l-phenyl-2- (3 ', 4'-dimethylphenyl) imidazole from m.p. 146 to 14700 (from ethyl alcohol).

The conversion is 85.9 percent, based on the starting material used IV. The yield remains constant even after 72 hours.

Example 5 100 parts of 1-phenyl-2-cyclohexylimidazoline and 50,000 parts by volume Nitrogen are passed every hour through the fluidized bed reactor heated to 35,000. The output from the reactor is fractionated via a column and obtained at a Kp0 >> 1180C 77.5 parts of l-phenyl-2-cyclohexylimidazole, corresponding to a yield of 83.6% of theory, based on converted starting material IV.

The conversion is 93.6 percent, based on the starting material used IV. The yield remains constant even after 72 hours of operation.

Claims (1)

Process for the production of imidazoles of the formula Verrahren zur Herste wherein R1, R2, R3 and R4 can be identical or different and each denote an aliphatic, cycloaliphatic, araliphatic or aromatic radical, R1, R2, R3 can also denote a hydrogen atom, according to the procedure for the preparation of imidazoles of the formula where R1 and R2 have the abovementioned meaning and R5 denotes a hydrogen atom, an aliphatic, araliphatic or aromatic radical, by reaction of 2-imidazolines of the formula wherein R1, R2 and R5 have the aforementioned meaning, reacted at a temperature of 300 to 6000C in the presence of zinc oxide or a mixture of zinc oxide and aluminum oxide as catalysts, according to patent application P 27 29 017.1 and P 27 28 976.5, characterized in that one instead of the starting materials III 2-imidazolines of the formula in which R1, R2, R3 and R4 are as defined above.