Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
  • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
  • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
  • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
  • C07D213/72—Nitrogen atoms
  • C07D213/73—Unsubstituted amino or imino radicals

Definitions

• This invention relates to the manufacture of a diaminopyridine, such as 2 , 6-diaminopyridine and related compounds, which are used industrially as precursors and intermediates in the synthesis of a variety of useful materials .
• Another process for manufacturing a diaminopyridine is a three step transformation of epichlorohydrin. This process has generally low productivity, and requires the use of excess sodium cyanide and handling of HCN. In addition, purification of the intermediate hydroxyglutaronitrile is required to achieve acceptable yields of the DAP product.
• Displacement of chlorines with ammonia or amines in dichloropyridines is known.
• One method for example, manufactures aminopyridines from chloropyridines and ammonia in the presence of a copper sulfate catalyst, and is described in Rec. Trav. Chim. , 58, 709-721 (1939) and DE No. 510,432. Yields in this process, however, are typically too low for commercial viability.
• aminopyridines are prepared by treating chloropyridines that contain at least one chlorine atom in the 2- or 6-position of the pyridine nucleus with aqueous NH 3 in the presence of metallic Cu or Al.
• the relatively large amounts of copper or aluminum powder, and the relatively high temperatures and pressures, needed to run this reaction make it undesirably difficult, and the yields of 2, 6-diaminopyridine are, again, generally too low for commercial viability.
• R 1 and R 2 in Formula (I) and in Formula (II) are each independently selected from the group consisting of
• synthesis of a diaminopyridine proceeds by means of chlorine-ammonia displacement in the presence of a copper source.
• DAP diaminopyridine
• R 1 and R 2 in Formula (I) and in Formula (II) are each independently selected from the group consisting of
• R is an alkyl, aryl or aralkyl radical
• the alkyl radical may be a C 1 - C 20 straight-chain, branched or cycloalkyl radical.
• suitable alkyl radicals include methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, n-pentyl, n-hexyl, cyclohexyl, n-octyl, trimethylpentyl, and cyclooctyl radicals.
• the terra "aryl" denotes a univalent group whose free valence is to a carbon atom of an aromatic ring.
• the aryl moiety may contain one or more aromatic rings and may be substituted by inert groups, i.e. groups whose presence does not interfere with the reaction.
• suitable aryl groups include phenyl, methylphenyl, ethylphenyl, n-propylphenyl, n-butylphenyl, t-butylphenyl, biphenyl, naphthyl and ethylnaphthyl radicals.
• aralkyl denotes an alkyl group which bears an aryl group.
• suitable aralkyl radicals include benzyl (i.e. the C 6 H 5 CH 2 - radical) and phenylethyl (i.e. phenethyl, the C 6 H 5 CH 2 CH 2 - radical) .
• compounds as represented by the structure of Formula (I) are prepared by contacting compounds as represented by the structure of Formula (II) (hereinafter referred to as "chloroamino pyridine” or "CAP") with a copper source in a buffered aqueous ammonia solution to form a reaction mixture, and heating the reaction mixture.
• R 1 and R 2 may each be H.
• the compound as represented by the structure of Formula (II) is 2-amino-6- chloropyridine, and the compound as represented by the structure of Formula (I) as made by this process is 2,6- diaminopyridine.
• Compounds as represented by the structure of Formula (II) may be synthesized by, for example, amination of 2-chloropyridine as described in JP 59/053,910 (Koei Chemical Co., Ltd.); reaction of 3-hydroxyglutaronitrile with anhydrous HCl [Ferrarini et al, Journal of
• CAP is also available commercially, for example, from Sigma-Aldrich (St. Louis, Missouri) .
• the copper source may be elemental copper
• Cu(0) or a copper compound such as a Cu (I) compound or a Cu (II) compound, such as a Cu (I) salt or a Cu (II) salt, or mixtures thereof.
• copper compounds suitable for use herein include without limitation CuCl, CuBr, CuI, Cu 2 SO 4 , CuNO 3 , CuCl 2 , CuBr 2 , CuI 2 , CuSO 4 , and Cu (NO 3 ) 2.
• CuBr and CuI are especially preferred.
• the copper source is believed to function in the reaction as a catalyst. Acting as a catalyst, the copper source would not participate in the reaction in any manner in which it would be chemically altered, but it is believed nevertheless to modify one or more parameters of the reaction to thereby enhance product formation.
• the copper source is consequently provided to the reaction mixture in a catalytically-effective amount, i.e. an amount that will achieve such purpose.
• the amount of copper used in the reaction is typically about 0.5 to about 7 mol% based on the number of moles of Formula (II) compound present in the reaction mixture.
• Ammonia concentration typically ranges from about 5 to about 10 moles per mole of Formula (II) compound present in the reaction mixture.
• the aqueous ammonia solution may be buffered by the addition thereto of a buffering agent.
• the buffering agent is a material that does not participate directly in the reaction but does by its presence limit the pH of the reaction mixture to a preselected limit.
• the buffering agent is frequently a material that, in the context of a Br ⁇ nsted-Lowry acid, is a weak acid/conjugate base pair, or a weak base/conjugate acid pair.
• the buffering agent will, in attaining an equilibrium by the gain or loss of protons, limit changes in the pH of the reaction mixture to a preselected range in relation to events such as the addition to the system of acid or alkali, or dilution of the reaction mixture.
• a buffering agent to the reaction mixture hereof creates a buffered solution in which the pH will be maintained at a pH of about 4.0 or more, about 4.5 or more, about 5.0 or more, or about 5.5 or more, and yet about 8.0 or less, about 7.5 or less, about 7.0 or less, or about 6.5 or less.
• the range of pH to which the buffering agent will limit the reaction mixture may be expressed in terms of any range formed any combination of the various maxima and minima, as set forth above.
• the buffering agent may be selected, for example, from among the alkali metal, the alkaline earth metal or the ammonium phosphates, borates, sulphates, carbonates, bicarbonates, acetates, hydroxides, bromides, silicates, citrates, gluconates and tartrates; or an alkali metal salt of a lower alkanecarboxylic acid, such as acetic acid; or a basic alkali metal salt of phosphoric acid.
• buffering agents also include without limitation sodium bicarbonate, sodium carbonate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium tetrapyrophosphate, orthophosphates and the water-soluble condensed phosphates such as tripolyphosphates and pyrophosphates. Also included are ammonium acetate, ammonium bromide, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, and ammonium borate.
• alkali metal compounds or alkaline earth metal compounds such as the sodium, potassium and calcium compounds, and, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, and potassium carbonate, calcium carbonate, sodium acetate, disodium hydrogen phosphate, trisodium phosphate and sodium borate.
• the buffering agent may be added to the reaction mixture in any convenient manner.
• an ammonium salt of a weak acid is used as the buffering agent
• the salt may be added directly as the salt (e.g. ammonium acetate) or may be formed in situ (e.g. by adding acetic acid or acetic anhydride to excess aqueous ammonia) .
• the buffering agent is present in the reaction mixture at a concentration of from about 20 to about 60 wt% based on the weight of the whole reaction mixture .
• reaction conditions such as temperature, pressure and time may vary according to the choice of the specific copper source, the following conditions have typically been found suitable to achieve production of a desired Formula (I) compound: a heated reaction temperature generally in the range of from about 100°C to about 150°C; a reaction pressure generally in the range of from about 150 psi (1.03 MPa) to about 700 psi (4.83 MPa); and a reaction time generally in the range of about 5 to about 9 hours.
• the DAP reaction product of the process hereof is separated from the reaction mixture by removal of excess ammonia and part of the water followed by crystallization from the reaction mixture that contains the reaction product, the buffering agent and the catalyst.
• the reaction product is separated by precipitating it as a hemisulfate by adding sulfuric acid to the reaction mixture.
• the process hereof advantageously provides an increased selectivity to, and yield of, the desired Formula (I) product as compared to known processes.
• selectivity for a product (“P") denotes the molar fraction or molar percentage of P in the final product mix
• conversion denotes how much reactant was used up as a fraction or percentage of the theoretical amount .
• the conversion multiplied by the selectivity thus equals the maximum “yield” of P, while the actual yield, also referred to as “net yield, " will normally be somewhat less than this because of sample losses incurred in the course of activities such as isolating, handling, drying, and the like.
• the term "purity" denotes what percentage of the in-hand, isolated sample is actually the specified substance.
• the increased selectivity to, and yield of, the desired Formula (I) product obtained herein may result from what appears to be the effect of the buffering agent to minimize the occurrence of undesirable side reactions, thereby resulting in an increase in selectivity to the desired product.
• the invention is not, however, limited to any particular theory of operation.
• a diaminopyridine may be made by a process such as described above, and then further subjected to a polymerization reaction to prepare an oligomer or polymer therefrom, such as those having the type of functionality named above.
• a polymer such as pyridobisimidazole-2, 6-diyl (2, 5-dihydroxy-p-phenylene) polymer may also be prepared from a diaminopyridine.
• a diaminopyridine may be converted into a polyamide oligomer or polymer by reaction with a diacid (or diacid halide) in a process in which, for example, the polymerization takes place in solution in an organic compound that is liquid under the conditions of the reaction, is a solvent for both the diacid (halide) and the diaminopyridine, and has a swelling or partial salvation action on the polymeric product.
• the reaction may be effected at moderate temperatures, e.g. under 100°C, and is preferably effected in the presence of an acid acceptor that is also soluble in the chosen solvent.
• Suitable solvents include methyl ethyl ketone, acetonitrile, N,N- dimethylacetamide dimethyl formamide containing 5% lithium chloride / and N-methyl pyrrolidone containing a quaternary ammonium chloride such as methyl tri-n-butyl ammonium chloride or methyl-tri-n-propyl ammonium chloride.
• a quaternary ammonium chloride such as methyl tri-n-butyl ammonium chloride or methyl-tri-n-propyl ammonium chloride.
• a diaminopyridine may also be converted into a polyamide oligomer or polymer by reaction with a diacid (or diacid halide) in a process in which, for example, a solution of the diaminopyridine in a solvent may be contacted in the presence of an acid acceptor with a solution of a diacid or diacid halide, such as a diacid chloride, in a second solvent that is immiscible with the first to effect polymerization at the interface of the two phases.
• the diaminopyridine may, for example, be dissolved or dispersed in a water containing base with the base being used in sufficient quantities to neutralize the acid generated during polymerization- Sodium hydroxide may be used as the acid acceptor.
• Preferred solvents for the diacid (halide) are tetrachloroethylene, methylenechloride, naphtha and chloroform.
• the solvent for the diacid (halide) should be a relative non-solvent for the amide reaction product, and be relatively immiscible in the amine solvent.
• a preferred threshold of immiscibility is as follows: an organic solvent should be soluble in the amine solvent not more than between 0.01 weight percent and 1.0 weight percent.
• the diaminopyridine, base and water are added together and vigorously stirred. High shearing action of the stirrer is important.
• the solution of acid chloride is added to the aqueous slurry.
• Contacting is generally carried out at from 0 c C to 60°C, for example, for from about 1 second to 10 minutes, and preferably from 5 seconds to 5 minutes at room temperature. Polymerization occurs rapidly. Processes similar to the foregoing are described in US 3,554,966 and US 5,693,227.
• a diaminopyridine may also be converted into a polyimide oligomer or polymer by reaction with a tetraacid (or halide derivative thereof) or a dianhydride in a process in which each reagent (typically in equimolar amounts) is dissolved in a common solvent, and the mixture is heated to a temperature in the range of 100 ⁇ 250°C until the product has a viscosity in the range of 0.1 ⁇ 2 dL/g.
• Suitable acids or anhydrides include benzhydrol 3, 3', 4,4'- tetracarboxylic acid, 1,4-bis (2,3-dicarboxyphenoxy) benzene dianhydride, and 3, 3' , 4, 4' -benzophenone tetracarboxylic acid dianhydride.
• Suitable solvents include cresol, xylenol, diethyleneglycol diether, gamma-butyrolactone and tetramethylenesulfone.
• a polyamide-acid product may be recovered from the reaction mixture and advanced to a polyimide by heating with a dehydrating agent such as a mixture of acetic anhydride and beta picoline. Processes similar to the foregoing are described in US 4,153,783; US 4,736,015; and US 5,061,784.
• a diaminopyridine may also be converted into a polyurea oligomer or polymer by reaction with a polyisocyanate, representative examples of which include toluene diisocyanate; methylene bis (phenyl isocyanates) ; hexamethylene diisocycanates; phenylene diisocyanates.
• the reaction may be run in solution, such as by dissolving both reagents in a mixture of tetramethylene sulfone and chloroform with vigorous stirring at ambient temperature.
• the product can be worked up by separation with water, or acetone and water, and then dried in a vacuum oven.
• the polyurea forming reaction may also be run under interfacial conditions, such as by dissolving the diaminopyridine in an aqueous liquid, usually with an acid acceptor or a buffer.
• the polyisocyanate is dissolved in an organic liquid such as benzene, toluene or cyclohexane.
• the polymer product forms at the interface of the two phases upon vigourous stirring.
• Processes similar to the foregoing are described in US 4,110,412 and Millich and Carraher, Interfacial Syntheses, vol. 2, Dekker, New York, 1977.
• a diaminopyridine may also be converted into a polyurea by reaction with phosgene, such as in an interfacial process as described in US 2,816,879.
• a diaminopyridine may also be converted into a pyridobisimidazole-2, 6-diyl (2, 5-dihydroxy-p-phenylene) polymer by (i) converting the diaminopyridine to a diamino dinitropyridine, (ii) converting the diamino dinitropyridine to a tetraamino pyridine, and (iii) converting the tetraamino pyridine to a pyridobisimidazole- 2, 6-diyl (2, 5-dihydroxy-p-phenylene) polymer.
• a diaminopyridine may be converted to a diamino dinitropyridine by contacting it with nitric acid and a solution of sulfur trioxide in oleum, as discussed in WO 97/11058.
• a diamino dinitropyridine may be converted to a tetraamino pyridine by hydrogenation using a hydrogenation catalyst in the presence of a strong acid, and using a cosolvent such as a lower alcohol, an alkoxyalcohol, acetic acid or propionic acid, as discussed in US 3,943,125.
• a tetraamino pyridine may be converted to a pyridobisimidazole-2, 6-diyl (2, 5-dihydroxy-p-phenylene) polymer by polymerizing a 2, 5-dihydroxyterephthalic acid with the trihydrochloride-monohydrate of tetraaminopyridine in strong polyphosphoric acid under slow heating above
• the pyridobisimidazole-2, 6-diyl (2, 5-dihydroxy-p-phenylene) polymer so produced may be, for example, a poly (1,4- (2, 5- dihydroxy) phenylene-2, 6-pyrido [2, 3-d: 5,6- d 1 Ibisimidazole) polymer, or a poly [ (1,4- dihydrodiimidazo [4, 5-b:4' , 5' -e]pyridine-2, 6-diyl) (2, 5- dihydroxy-1,4-phenylene) ] polymer.
• the pyridobisimidazole portion thereof may, however, be replaced by any or more of a benzobisimidazole, benzobisthiazole, benzobisoxazole, pyridobisthiazole and a pyridobisoxazole; and the 2,5- dihydroxy-p-phenylene portion thereof may be replace the derivative of one or more of isophthalic acid, terephthalic acid, 2,5-pyridine dicarboxylic acid, 2, 6-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 2,6- quinoline dicarboxylic acid, and 2,6-bis(4- carboxyphenyl) pyridobisimidazole.
• the reaction mixture was allowed to cool to room temperature, and the pressure was brought back to atmospheric pressure.
• the reaction mixture was analyzed using a quantitative GC analytical method.
• the conversion of 2-amino-6- chloropyridine was 99.0%.
• the yield for 2,6- dichloropyridine was 81%.
• range includes the endpoints thereof and all the individual integers and fractions within the range, and also includes each of the narrower ranges therein formed by all the various possible combinations of those endpoints and internal integers and fractions to form subgroups of the larger group of values to the same extent as if each of those narrower ranges was explicitly recited.
• range of numerical values is stated herein as being greater than a stated value, the range is nevertheless finite and is bounded on its upper end by a value that is operable within the context of the invention as described herein.
• range of numerical values is stated herein as being less than a stated value, the range is nevertheless bounded on its lower end by a non-zero value.

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