Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C271/00—Derivatives of carbamic acids, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
  • C07C271/06—Esters of carbamic acids

Definitions

• This invention relates to improvements in the preparation of aromatic urethanes. More particularly, it relates to an improved process for preparing an aromatic urethane (hereinafter referred to simply as “urethane") which comprises reacting an aromatic nitro compound, an organic compound containing at least one hydroxyl group (hereinafter referred to simply as “hydroxyl-containing compound”), and carbon monoxide at elevated temperature and pressure in the presence of a catalytic system composed of a catalyst selected from the group consisting of platinum group metals, compounds of platinum group metals and mixtures thereof and a promoter selected from the group consisting of
• U.S. Patent No. 3,338,956 describes a process wherein urethanes are prepared from alcohols, carbon monoxide, and nitro compounds with the aid of a rhodium chlorocarbonyl catalyst.
• this process is not economically advantageous in the preparation of highly pure urethanes because the desired product is obtained only at low yield even if the urethanation reaction is carried out for a long period of time in the presence of a large amount of the catayst.
• the invention relates therefore to a process for preparing an aromatic urethane wherein an aromatic nitro compound, an organic hydroxyl-containing compound having at least one hydroxyl group, and carbon monoxide are reacted with each other in the presence of a catalytic system at a temperature of from 80 to 230°C and a pressure of from 10 to 1000 kg/cm 2 G
• the process according to the invention is characterized in that the reaction is carried out in the presence of a catalytic system composed of a catalyst selected from the group consisting of platinum group metals, compounds of platinum group metals and mixtures thereof and a promoter selected from the group consisting of
• the urethanation reaction is carried out in the presence of a small amount of water and one or more of those organic primary amino compounds, urea compounds, biuret compounds, and allophanate compounds which can be derived from the starting aromatic compound.
• the starting aromatic nitro compound is a compound of the formula where A represents a substituted or unsubstituted aromatic residue of an aromatic nitro compound from which the nitro group or groups are removed and x is an integer equal to from 1 to 4
• the starting hydroxyl-containing compound is a compound of the formula where R i represents a linear or branched alkyl group containing from 1 to 16 carbon atoms, a cycloalkyl group of 6 carbon atoms with or without an alkyl substituent containing from 1 to 3 carbon atoms or an aryl group with or without at least one alkyl substituent containing from 1 to 6 carbon atoms
• these alkyl, cycloalkyl and aryl groups may further include at least one halogen, aryl, alkenyl, nitro, alkoxy, phenoxy or carbamate substituent, those organic primary amino compounds, urea compounds, biuret compounds, and allophanate compounds which can be derived from the starting aromatic nitro compound are represented
• a and x have the same meanings as defined in formula (V), R 1 has the same meanings as defined in formula (VI), y is an integer equal to from 1 to 4, z is an integer equal to from 0 to 3, and the sum of y and z does not exceed x.
• A' represents a group of the formula where A, R,, x, y and z have the same meanings as defined in formula (VII).
• the desired aromatic urethane can be prepared at a higher reaction rate, or in a shorter reaction time, than that attainable by the afore-mentioned processes. Morever, when one or more of those organic primary amino compounds, urea compounds, biuret compounds, and allophanate compounds which can be derived from the starting aromatic nitro compound are used, the yield of the desired aromatic urethane is enhanced. The yield based on the starting aromatic nitro compound can even reach a substantially theoretical level depending on the amount of the aforesaid compound or compounds added to the reaction system.
• reaction rate is further increased without reducing the yield of the desired product.
• the aromatic nitro compounds useful as the main starting material in the process of the invention are those represented by the formula where A and x have the same meanings as defined in formula (V), and may be mononitro and polynitro compounds. They include, for example, nitrobenzene, dinitrobenzenes, dinitrotoluenes, nitronaphtha- lenes, nitroanthracenes, nitrobiphenyls, bis(nitrophenyl)alkanes, bis(nitrophenyl)ethers, bis(nitrophenyl)-thioethers, bis(nitrophenyl)sulfones, nitrodiphenoxyalkanes, nitrophenothiazines, and heterocyclic compounds such as 5-nitropyrimidine.
• nitro compounds are nitrobenzene, o-, m-, and p-nitrotoluenes, o-nitro-p-xylene, 1-nitronaphthalene, m- and p-dinitrobenzenes, 2,4- and 2,6-dinitrotoluenes, dinitromesitylene, 4,4'-dinitrobiphenyl, 2,4-dinitrobiphenyl, 4,4'-dinitrodibenzyl, bis(4-nitrophenyl)methane, bis(4-nitrophenyl)ether, bis(2.4-dinitrophenyl)ether, bis(4-nitrophenyl)thioether, bis(4-nitrophenyl)sulfone, bis(4-nitrophenoxy)ethane, ⁇ , ⁇ '-dinitro-p-xylene, ⁇ . ⁇ '- dinitro-m-xylene, 2,4,6-trinitrotoluene, o-, m- and
• aromatic nitro compounds mononitro compounds such as nitrobenzene, o-, m- and p-chloronitrobenzenes, 2,3- and 3,4-dichloronitrobenzenes, etc. and dinitro compounds such as m- and p-dinitrobenzenes, 2,4- and 2,6-dinitrotoluenes, 1,5-dinitronaphthalene, etc. are preferred because they can be readily reacted with other reactants to give high yields of desired products which have wide applications in the manufacture of drugs, agricultural chemicals, polyurethanes, and the like.
• hydroxyl-containing compounds useful in the process of the invention are those represented by the formula where R, has the same meanings as defined in formula (VI), and n is an integer equal to or greater than 1 and preferably in the range of from 1 to 3. They include monohydric and polyhydric alcohols having one or more hydroxyl groups attached to primary, secondary or tertiary carbon atoms, as well as monohydric and polyhydric phenols.
• suitable alcohols are monohydric alcohols such as methyl alcohol, ethyl alcohol, n- and iso-propyl alcohols, n-, iso- and t-butyl alcohols, linear or branched amyl alcohol, hexyl alcohol, cyclohexyl alcohol, lauryl alcohol, cetyl alcohol, benzyl alcohol, chlorobenzyl alcohol, methoxybenzyl alcohol, etc.; dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, etc.; trihydric alcohols such as glycerol, hexanetriol, etc.; and further polyhydric alcohols.
• monohydric alcohols such as methyl alcohol, ethyl alcohol, n- and iso-propyl alcohols, n-, iso- and t-butyl alcohols, linear or branched amyl alcohol, hexyl alcohol, cyclohexyl alcohol, lau
• Suitable phenols are phenol, chlorophenol, cresol, ethylphenol, linear or branched propylphenol, butyl- and higher alkylphenols, catechol, resorcinol, 4,4'-dihydroxy-diphenylmethane, 2,2'-isopropylidenediphenol, anthranol, phenanthrol, pyrogallol, phloroglucinol, etc.
• methyl alcohol, ethyl alcohol, and isobutyl alcohol are preferred because they give higher yields of desired products at a higher reaction rate as compared with other hydroxyl-containing compounds.
• the catalysts useful in the process of the invention include, for example, elemental palladium, rhodium and ruthenium; the halides, cyanides, thiocyanides, isocyanides, oxides, sulfates, nitrates and carbonyl compounds of these metals; the addition products or complexes of these compounds with tertiary amines such as triethylamine, pyridine, isoquinoline, etc. and the complexes of these compounds with organic phosphorus compounds such triphenylphosphine, etc.; and mixtures of the foregoing.
• These catalysts may be used either by adding them directly to the reaction system or by associating them with carriers such as alumina, silica, carbon, barium sulfate, calcium carbonate, asbestos, bentonite, diatomaceous earth, fullers's earth, organic ion exchange resins, inorganic ion exchange resins, magnesium silicate, aluminum silicate, molecular sieve, and the like and then adding them to the reaction system.
• carriers such as alumina, silica, carbon, barium sulfate, calcium carbonate, asbestos, bentonite, diatomaceous earth, fullers's earth, organic ion exchange resins, inorganic ion exchange resins, magnesium silicate, aluminum silicate, molecular sieve, and the like and then adding them to the reaction system.
• these carriers may be added to the reaction system separately from the catalysts including elemental palladium, rhodium and ruthenium as well as compounds thereof.
• elemental palladium and palladium compounds are preferred. Specific examples are elemental palladium, palladium chloride, palladium bromide, and elemental palladium associated with a carrier such as carbon or alumina.
• the Lewis acids useful as the promoter in the process of the invention are, for example, those described in Jack Hine: “Physical Organic Chemistry” (McGraw-Hill Book Co., New York, 1962) and imply Bronsted acids. They include, for example, the halides, sulfates, acetates, phosphates, and nitrates of metals such as tin, titanium, germanium, aluminum, iron, nickel, zinc, cobalt, manganese, thallium, zirconium, copper, lead, vanadium, niobium, tantalum, mercury, etc.
• Lewis acids are ferric chloride, ferrous chloride, stannic chloride, stannous chloride, aluminum chloride, cupric chloride, cuprous chloride, copper acetate, etc.
• Lewis acids with tertiary amines also complexes of Lewis acids with tertiary amines and mixtures of Lewis acids and a complex of a Lewis acid with a tertiary amine and also a mixture of a tertiary amine and a complex of a Lewis acid with tertiary amines.
• Specific examples of the complex-forming tertiary amines are triethylamine, N,N-diethylaniline, N,N-diethylcyclohexylamine, 1,4-diazabicyclo[2,2,2]octane, pyridine, picoline, isoquinoline, quinoline, etc.
• nitrogen-containing heterocyclic compounds such as pyridine, picoline and isoquinoline are preferred.
• the use of'a complex derived from such a nitrogen-containing heterocyclic compound and a Lewis acid prevents the corrosion ot the reactor by the Lewis acid, enhances the yield of the desired product, and facilitates recovery of the catalyst, as compared with the use of the Lewis acid alone.
• the reaction rate is further increased by adding a small amount of water to the reaction system.
• the amount of water added should be from 1 to 70 moles of preferaby from 10 to 50 moles per 100 moles of the starting aromatic nitro compound. If the amount is less than 1 mole, the addition of water will be virtually ineffective, while if the amount is more than 70 moles, the yield of the desired product will be greatly reduced.
• the organic primary amino compounds useful in the process of the invention include, for example methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, ethylenediamine, propylenediamine, butylenediamine, hexanediamine, cyclohexylamine, cyclohexaldiamine, aniline, o-, m- and p-diaminobenzenes, 2-amino-4-carbamatetoluene, 4-amino-2-carbamatetoluene, 2-amino-6-carba- matetoluene, o-, m- and p-nitroanilines, 4-nitro-2-aminotoluene, 2-nitro-4-aminotoluene, 2-nitro-6-aminotoluene, 3-nitro-4-aminotoluene, 4-nitro-3-aminotoluene, 2-nitro-3-aminotoluene,
• aromatic amino compounds those which can be derived from the starting aromatic nitro compounds are preferred.
• nitrobenzene is used as the starting aromatic nitro compound
• aniline is preferred.
• 2-amino-4-nitrotoluene, 4-amino-2-nitrotoluene, 2-amino-4-carbamatetoluene, 4-amino-2-carbamatetoluene, and 2,4-diaminotoluene are preferably used when the starting aromatic nitro compound is 2,4-dinitrotoluene
• 2-amino-6-nitrotoluene, 2-amino-6-carbamatetoluene, and 2,6-diaminotoluene are preferably used when the starting aromatic nitro compound is 2,6-dinitrotoluene.
• urea compounds, biuret compounds, and allophanate compounds useful in the process of the invention are those represented by the respective formulae (VIII), (IX) and (X) in which, for example, A' is a phenyl group when the starting aromatic nitro compound is nitrobenzene or a tolyl group having a nitro, amino or carbamate group when the starting aromatic nitro compound is dinitrotoluene.
• Suitable solvents include, for example, aromatic solvents such as benzene, toluene, xylene, etc.; nitriles such as acetonitrile, benzonitrile, etc.; sulfones such as sulfolane, etc.; halogenated aliphatic hydrocarbons such as 1,1,2-trichloro-1,2,2-trifluorethane, etc.; halogenated aromatic hydrocarbons such as monochlorobenzene, dichlorobenzene, trichlorobenzene, etc.; ketones; esters; and other solvents such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc.
• aromatic solvents such as benzene, toluene, xylene, etc.
• nitriles such as acetonitrile, benzonitrile, etc.
• sulfones such as sulfolane,
• the hydroxyl-containing compound and carbon monoxide are preferably used in amounts equal to at least 1 mole per mole of the nitro group of the starting aromatic nitro compound.
• the amount of platinum group metal or platinum group metal compound used as the catalyst may vary widely according to the type thereof and other reaction conditions. However, on a weight basis, the amount of catalyst is generally in the range of from 1 x 10- 5 to 1 part, and preferably from 1 x 10- 4 to 5 x 10-' part, per part of the starting aromatic nitro compound when expressed in terms of its metallic component.
• the amount of Lewis acid used as the promoter is generally in the range of from 2 x 10- 3 to 2 parts, and preferably from 5 x 10- 2 to 1 part, per part of the starting aromatic nitro compund.
• the reaction temperature is held in the range of from 80° to 230°C, and preferably from 140° to 200°C.
• the reaction pressure is in the range of from 10 to 1,000 kg/cm 2 G, and preferably from 30 to 500 kg/cm 2 G.
• the reaction time depends on the nature of aromatic nitro compound used, the reaction temperature, the reaction pv :.;sure, the type and amount of catalyst used, the type and amount of organic primary amino compound, urea compound, biuret compound, or allophanate compound added, the type of reactor employed, and the like, but is generally in the range of from 5 minutes to 6 hours.
• the reaction mixture is cooled and the gas is discharged from the reactor.
• the reaction mixture is subjected to any conventional procedure including filtration, distillation, or other suitable separation steps, whereby the resulting urethane is separated from any unreacted materials, any by-products, the solvent, the catalyst, and the like.
• the urethanes prepared by the process of the invention have wide applications in the manufacture of agricultural chemicals, isocyanates, and polyurethanes.
• Example 2 The procedure of Example 1 was repeated except that the aniline was replaced by 0.7 g of diphenylurea (Example 2). In addition, the procedure of Example 1 was repeated except that the aniline was omitted (Control 1). The results of Example 2 and Control 1, together with those of Example 1, are summarized in Table 1 below.
• Example 3 The procedure of Example 3 was repeated except that the isopropylamine was replaced by a variety of primary amino compounds and urea compounds (Examples 4-11). In addition, the procedure of Example 3 was repeated except that the isopropylamine was omitted (Control 2). The results of Examples 4-11 and Control 2 are summarized in Table 2 below.
• Example 3 The procedure of Example 3 was repeated except that the ethanol was replaced by 68 ml of isobutanol and the isopropylamine was replaced by 0.8 g of 2-amino-4-isobutylcarbamatetoluene and 0.8 g of 4-amino-2-isobutylcarbamatetoluene. After 160 minutes of reaction, the yield of diurethane was 99%.
• Example 13 The procedure of Example 13 was repeated except that the aminoethylcarbamatetoluenes were omitted. The reaction was carried out for the same period of time, or 120 minutes, as in Example 13. Analysis of the resulting solution revealed that the starting 2,4-dininitrotoluene was absent but the yield of mononitromonourethane was 15% and that of diurethane was 80%.
• Example 14 The procedure of Example 14 was repeated except that the allophanate compound was replaced by 1.4 g of a biuret compound (formed by heating a mixture of 2,4-toluene diisocyanate and water). The absorption of carbon monoxide ceased in 120 minutes. Analysis of the resulting solution revealed that the yield of diurethane was 97%.

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