DD268934A1 - PROCESS FOR THE PREPARATION OF N-ARYLCARBAMATES - Google Patents

Abstract

The aim of the invention is a further improved process for the economical production of N-aryl carbamates which works without phosgene and which extracts N-aryl carbamates from the nitroaromatics in a one-stage process in the presence of more efficient catalysts based on sulfur and sodium and / or potassium vanadates. Where the N-aryl carbamates are formed in good selectivity largely independent of the alcohol used, if the total amount of sulfur is only a maximum of 10 mol% per nitro group of the nitroaromatic used. For this purpose, nitroaromatics are reacted with alcohols and carbon monoxide under substantially anhydrous conditions in the presence of sulfur and / or sulfur compounds and sodium and / or potassium vanadate in combination with cyclic polyethers preferably crown ethers.

Description

Field of application of the invention

The invention relates to an improved process for the preparation of N-aryl carbamates by reacting nitroaromatics with alcohols and carbon monoxide in the presence of a new, more efficient catalyst system. N-Arylcarbamate are active ingredients in pesticides and starting materials for pesticides and polyurethane production.

Characteristic of the known technical solutions

N-aryl carbamates are produced industrially by reacting alcohols with aryl isocyanates, which are obtained by phosgenation of arylamines. Arylamines are accessible by reduction of the corresponding nitroaromatics. The use of toxic phosgene and thus of chlorine, which does not appear in the final product, makes this three-stage process more expensive and entails special corrosion and environmental problems. Therefore, it has long been attempted to prepare N-aryl carbamates directly from nitroaromatics, alcohols and carbon monoxide in order to avoid the problems mentioned with this more economical one-step process.

Many methods such. For example, DE-OS 2,342,458, DE-OS 2,555,557, DE-OS 2,603,574 use noble metal-containing catalyst systems that are technically not applicable, since significant losses of expensive catalysts occur and relatively expensive, largely hydrogen-free carbon monoxide is needed to lead this process selectively. The process according to DE-OS 2,343,826 uses selenium and / or sulfur or compounds of these elements in combination with bases such as amines and alkali metal carboxylates as catalyst system. However, N-aryl carbamates are selectively formed only with selenium-containing catalysts. By-products are always arylamines and Ν, Ν'-diarylureas. Arylamines become the major product when using hydrous alcohol or sulfur-based catalysts. Subsequent variants of this method (DE-OS 2,614,101, DE-OS 2,623,694, DE-OS 2,808,980 and DE-OS 2,808,990) work with special bases and other additives. As catalyst components, i.a. Acyclic amidines, phenols, carboxylic acids, alkali metal iodides, cyanides, -rhcdanide, oxidizing agents and even the already formed N-arylamines and Ν, Ν'-diaryl ureas described. All of these processes have the disadvantage that N-aryl carbamates are formed selectively selectively only with selenium-containing catalysts. These catalysts are also expensive and considerable selenium losses can only be avoided with extreme technological effort. The use of selenium is toxicologically questionable even in small amounts, since various organoselen compounds are formed which adhere to the N-aryl carbamates, give them an unpleasant odor and prohibit their use as plant protection products. Therefore, DE-OS 2,838,754 has described an improved process which is only suitable with sulfur-containing multicomponent catalyst systems

Achieved N-Arylcarbamatselektivitäten. The main disadvantage of this method is the necessary amount of elemental sulfur and / or sulfur compound. The stated in cJ ^ n embodiments of DE-OS 2,838,754 total amount of sulfur and / or sulfur compound is 14.6 to 52 mol% of the nitrobenzene used, but usually 37 mol% l

Also unfavorable is the total amount of all catalyst components, which is often more than 50 wt .-% of the nitrobenzene used. This and the diversity of the heterogeneous and homogeneous catalyst components complicates the separation and purification processes. The catalyst system consists, for example, of sulfur and / or a sulfur compound, aniline, a potassium salt, an iron oxide-vanadium oxide mixture and a secondary aliphatic amine. Recently, the use of alkali metal vanadates together with sulfur and / or sulfur compounds as catalyst has been found to provide an improved process that utilizes simple, commercial and inexpensive catalysts and provides N-aryl carbamates in good selectivity when the total sulfur level is only a maximum of 10 mole percent per nitro group of the respective nitroaromatic.

Surprisingly, we have now found that the effectiveness of this catalyst must be further improved. It has been shown that methyl and ethyl-N-arylcarbamate from nitroaromatics, methanol or ethanol and carbon monoxide arise only with the use of expensive cesium vanadates in sufficiently good selectivity. However, when using the cheap and commercially available sodium and potassium vanadates, this is limited to E'.hyl-N-arylcarbamate synthesis in the presence of potassium vanadates. The sodium and Kaliumvanadatkatalysatoren are particularly in the production of N-aryl carbamates higher alcohols such. As the crop protection agent isopropyl-N-phenylcarbamate (IPC) only slightly effective if no special and expensive solvents are used.

Object of the invention

The aim of the invention is a further improved process for the economical production of N-aryl carbamates which operates without phosgene and which extracts N-aryl carbamates from the nitroaromatics in a one-stage process.

Explanation of the essence of the invention

The invention has for its object to develop a process for the preparation of N-aryl carbamates from nitroaromatics, alcohols and carbon monoxide, which works with more efficient catalysts based on sulfur and / or sulfur compounds and sodium and / or potassium vanadate and N-aryl carbamates in good selectivity largely independent of the alcohol used when the total amount of sulfur is only a maximum of 10 mol% per nitro group of the nitroaromatic used.

According to the invention the object is achieved in that Nitroaromatcr; be reacted with alcohols and carbon monoxide under substantially anhydrous conditions in the presence of sulfur and / or sulfur compounds, characterized in that one uses catalyst systems containing as components sodium and / or potassium vanadates of the general formula

M _k V, O _m · (H ₂ O) _n M = Na, K

k, l, m, n = integer indices with k, l-1, m § 3, η S Oin preferably contain crown ethers in combination with cyclic polyethers. Examples of such sodium and potassium vanadates are sodium metavanadate (NaVO ₃ ), potassium metavanadate (KVO ₃ ), N'itriumorthovanadat (Na ₃ VO ₄ ), potassium orthovanadate (K ₃ VO ₄ ) and their hydrates and all intermediate forms corresponding to the general formula wherein preferably the hydrate-anhydrous sodium and potassium vanadates are used. Suitable cyclic polyethers for the process according to the invention are the crown ethers, neutral cyclic compounds having from 5 to 10 oxygen atoms in the ring, between which in each case preferably 2 carbon atoms are located. Examples of suitable cyclic polyethers are the following crown ethers: III.10.-pentaoxa-cyclopentadecane (15) crown-r) / 1 /, 2, 5, 8, 11, 14-pentaoxa-bicyclo-iso-oladeca-1-ol. ie.iS-tri-benzo-HSi-crown-S), 1,4,7,10,13,16-hexaoxa-cyclooctadecane ([18] krono-6), 2,3,11,12-tetraphenyl-1,4,7 , 10,13,16-hexaoxa-cyclooctadecane (tetraphenyl [18] crown-6), 2,5,8,15,18,21-hexaoxa-tricyclo | 20.4.0.0 ⁹ - ¹⁴ lhexacosa-9 (14), 10,12,22 (1), 23,25-hexaen (dibenzo [18] crown-6), 2,5,8,15,18,21-H6xaoxatricyclo [20.4.0.0 ^9M ] hexacosan (dicyclohexano- | ) crown-6), 2,5,12,15,22,25-hexaoxa-tetracyclo [24.4.0.0 ^{e '11} O' ⁶² '] triaconta-6 (11), 7, 9, 16 (21), 17,19,26 (1), 27,29-nonaen (Tribenzo- [18] crown-6).

Sulfur and / or sulfur compounds are necessary components of the catalyst system. Suitable for the process according to the invention are, for example, sulfur in any elemental form, carbonoxysulfide (COS), and organic and inorganic sulfur compounds which form in situ under the reaction conditions and with the reactants or other catalyst components of the process according to the invention carbonoxisulfide (COS) such. As alkali metal sulfides, alkali metal sulfides, alkali metal polysulfides and their analogous ammonium sulfide compounds, the ammonium NHi but may also be a cationic organic nitrogen compound, hydrogen sulfide, dialkyl, Diaralkylsulfide or disulfides, organic thiocarbonates ν nd thiocarbamates and thiourea and substituted thioureas. From an economic point of view, it is preferred to use elemental sulfur, finely ground or, in other finely divided form, possibly also on suitable carrier materials.

Starting compounds for the process according to the invention are:

1. Nitroaromatics, such as all substituted and unsubstituted aromatic mono-, di- and Polynitroverbindungon preferably having 6 to 20 carbon atoms per molecule. Examples of such nitroaromatics are nitrobenzenes, nitronaphthalenes, nitrotoluenes, nitrochlorobenzenes, nitroxylenes, nitrodichlorobenzenes, nitrochlorotoluenes, nitrocumines, nitromesitylene,

1 In the following text, the trivial names (the so-called crown names) are used in ((- nomenclature names).

Dinitrotoluenes, dinitrochlorobenzenes, dinitroxylenes, dinitromesitylene, dinitrodiphenyls, dinitrophenyl ethers, dinitrodiphenylmethanes, trinitrodiphenylmethanes and tetranitrodiphenylmethanes. Aromatic di- or polynitro compounds whose nitro groups have already been partly converted into carbamate groups can also be used as starting compounds, such as, for example, ethyl N (3-nitro-4-methylphenyl) carbamate and ethyl N- (5-nitro-2-) methylphenyl) carbamate, which may occur as products of incomplete reaction of 2,4-dinitrotoluene with ethanol and carbon monoxide. Such nitroaromatics are used as starting compounds especially when the process according to the invention is carried out continuously in the circulation or batchwise, batchwise and incompletely reacted aromatic di- or polynitro compounds are recycled back into the process.

2. Alcohols, such as all aliphatic, cycloaliphatic and araliphatic alcohols having preferably 1 to 20 carbon atoms per molecule, which have a hydroxyl group on a primary, secondary or tertiary carbon atom and whose other molecular radical is inert under the reaction conditions. Examples of such alcohols are methanol, ethanol, n-propanol, iso-propanol, all isomeric butanols, pentanols, hexanols, heptanols, octanols, etc. Cyclohexanol, benzyl alcohol, and the like. Preferably, methanol, ethanol, n- and iso-propanol are used in the process according to the invention.

3. Gaseous carbon monoxide. It is essential for the efficiency of the process according to the invention that no special requirements have to be made of the purity of the carbon monoxide. The carbon monoxide should be anhydrous, but may contain some CO ₂ , 0 ₂ , inert gas and also hydrogen. Even 10% by volume of H ₂ in the carbon monoxide have no negative influence on the reaction.

The mixture of the three starting materials and the catalyst system forms the reaction mixture of the process according to the invention, in which, in a simple embodiment, the alcohol is reactant and solvent. In this case, the alcohol is used in such amounts that for each nitro group of the nitro aromatic used 8 to 50 hydroxyl groups of the alcohol used are present. In another embodiment of the process according to the invention, nitroaromatic and alcohol are dissolved in an inert solvent in which the catalyst is also dissolved or suspended. In this case, the alcohol is used in such amounts that for each nitro group of the nitroaromatic used 1.2 to 15 hydroxyl groups of the alcohol used:. available. To convert a nitro group, 3 moles of carbon monoxide are needed. Practically, however, one always works with an excess of carbon monoxide. The reaction mixture of the process according to the invention may contain, in addition to the starting materials and the components of the catalyst system, further substances, for example the by-products which are formed during the reaction, such as arylamines, N-arylformamides, N, N'-diarylureas, azo and azoxy compounds. Their presence in the reaction mixture is given especially when the process according to the invention is carried out continuously in the circulation or batchwise, batchwise with partial recycling of the reaction solution. The presence of such by-products is not the subject of the invention since it has been found that the results of the reaction of the process according to the invention thereof are not or only insignificantly influenced.

For the process according to the invention, the sulfur and / or the sulfur compounds are used in amounts such that the total amount of sulfur is 5 to 10 mol% per nitro group of the nitroaromatic used.

The alkali metal vanadates are used in amounts such that the amount of vanadium in the reaction mixture is 5 to 20 mol% per nitro group of the nitroaromatic used.

The crown ethers are used in amounts such that their concentration is 0.5 to 20 mol% per nitro group of the nitroaromatic used.

In the embodiment of the process according to the invention which uses an inert solvent, preference is given to using polar aprotic solvents having sufficient dissolving power for the alkali metal vanadates, such as acetonitrile, tetramethylurea, dialkylsulfoxides, sulfones, dimethylformamide, N-methyloxazolone, esters and ketones.

All components of the reaction mixture of the process according to the invention can be added to the reaction vessel in an optional order. The order of the assignment depends on the particular embodiment and the apparatus used.

A suitable discontinuous embodiment of the process according to the invention consists for example in that nitroaromatic, alcohol and optionally a solvent are placed together with the catalyst components in an autoclave, the material must be inert to all components of the reaction mixture under the reaction conditions or contains the corresponding linings or inserts , Then carbon monoxide is introduced under pressure and stirred or shaken while warming. Carbon monoxide can be continuously replenished during the reaction.

A suitable continuous embodiment of the process according to the invention consists, for example, of reacting the reactants and the catalyst components during the passage through a pressure reaction tube or a reaction vessel cascade. The reaction temperature is generally maintained in the range of 120 to 220 ° C.

The reaction pressure is generally between 10 and 35 MPa. The reaction time is dependent on the particular nitroaromatic, the alcohol, the reaction temperature, the reaction pressure, the Katalysatorytem and the amount of the catalyst components and is about 15 minutes to 4 hours. After the reaction, the reaction mixture is cooled to room temperature and the reaction mixture is decompressed. To obtain the N-aryl carbamates, the liquid reaction mixture is subjected to suitable separation operations such as filtration, extraction, distillation or crystallization.

Recoverable, usable reaction components (catalyst components, alcohol and others) are reused.

The inventive method has the advantage that a sufficiently selective formation of N-aryl carbamates in a one-step process of nitroaromatics, alcohols and carbon monoxide in the presence of a more efficient catalyst based on sulfur and sodium and / or potassium is possible if the total amount of sulfur only a maximum of 10 mol% per nitro group of the nitroaromatic used.

The invention will be explained below with reference to 8 exemplary embodiments and 4 comparative examples.

-4- 268 Embodiment 1

0.45 mmol of finely ground sulfur (14.4 mg), 0.45 mmol of sodium metavanadate (NaVO ₃ , 55 mg) and 0.225 mmol of (15) Krone-5 (50 mg) were combined with ³ cm ^{3 of} 1.5 M nitrobenzene in absolute ethanol in one special glass vessel placed in a 25-cm ³ -Edelstahlautoklav. The sealed autoclave was purged 3 times with about 5 MPa of ultrapure carbon monoxide, and then high purity carbon monoxide was introduced to the initial pressure of 24.5 MPa. The autoclave was placed in a heating block heated at 180 ° C and agitated by a shaker. The pressure increased during the reaction to 29.1 MPa. After 2 hours, the autoclave was removed from the heating block and cooled. After relaxing and opening, the contents of the glass insert were analyzed by high-pressure liquid chromatography. The analysis showed:

Residual concentration c _N b = 0.01 M,

Ethyl N-phonylca-bamate concentration c _£ pc = 1.26M,

Aniline concentration c _A = 0.26M,

Ν, Ν'-diphenylurea concentration c _O ph = 0.03 M.

Comparative Example 1

Embodiment 1 was repeated without crown ether. The initial pressure was 24.5 MPa, the reaction pressure

HPLC analysis showed: c _NB = 1.06 M,

c _E pc = 0.25 M, c _A = 0.17 M, c _DPH = 0.02 M.

Embodiment 2

Example 1 was repeated by using 0.1125 mmol of dibenzo [18] crown-6 (40.5 mg) instead of [15] crown-5. The reaction pressure was 28.9 MPa. The HPLC analysis was: c _NB = 0.48 M, c _EPC = 0.82 M, c _A = 0.19 M, c _DPH = 0.07 M.

Embodiment 3

Embodiment Example 3 was carried out to prepare methyl N-phenylcarbamate (MPC) using Embodiment 1 with 0.225 mmol of dibenzo [18] crown-6 (81 mg) instead of the [15] crown-5 and ³ cm ³ 1, 5 M nitrobenzene was repeated in absolute methanol instead of the ethanolic solution. The reaction pressure was 30.4 MPa. The HPLC analysis showed complete conversion of the nitrobenzene and cmpc = 1.25 M, Ca-0.31 M, c _O ph = 0.02 M and a formanilide concentration c _fA = 0.02 M.

Comparative Example 2

Embodiment 3 was repeated without crown ether. The reaction pressure was 28.0 MPa. The HPLC analysis showed:

c _NB = 0.69 M, c _M pc = 0.63 M, c _A = 0.23 M, c _DPH = 0.02 M, c _FA = 0.01 M.

Embodiment 4

Embodiment 3 was repeated by using a carbon monoxide with 10% by volume of H ₂ instead of high-purity carbon monoxide. The starting pressure was 27.4 MPa, the reaction pressure 32.4 MPa. The HPLC analysis revealed: _NB c = 0.03 M, CMPC = 1.24 M, c _A = 0.28 M, 0.02 M c = _DPH, c _FA = 0.03 M.

Embodiment 5

Example 3 was repeated using crown-6 (60 mg) instead of NaVO ₃ and the dibenzo- [18] -rono-6 0.45 mmol potassium metavanadate (KVO ₃ , 62 mg) and 0.225 mmol [18]. The reaction pressure was

HPLC analysis revealed: c _NB = 0.05 M, c _M pc = 1.22 M, c _A = 0.28 M, c _DPH = 0.03 M, c _FA = 0.02 M.

Verglelchsbelsplel 3

Embodiment 5 was repeated without crown ether. The reaction pressure was 27.1 MPa. The HPLC analysis showed:

c _NB = 1.22 M, c _M pc = 0.1OM, c _A = 0.18M, c _DPH = 0.01M, c _FA = 0.01M.

Embodiment 6

Embodiment j was repeated by using a carbon monoxide with 10% by volume of H ₂ instead of high-purity carbon monoxide. The initial pressure was 26.5 MPa, the reaction pressure 28.4 MPa. HPLC analysis showed: c _NR = 0.02, Cmpc = 1.26 M, c _A = 0.25 M, c _DPH = 0.03 M, c _FA = 0.03 M.

-5- 268 934 Embodiment 7

Embodiment 7 was carried out to prepare isopropyl N-phenylcarbamate (IPC) by repeating Example 5 with ³ cm ^{3 of} 1.5 M nitrobenzene in absolute isopropanol instead of the methanolic solution. The reaction pressure was 28.7 MPa, the reaction time 2 hours and 10 minutes. The HPLC analysis revealed: c _Nfl = 0.02 M, CIPC = 1.14 M, c _A = 0.41 M, pH = 0-03 c _O M.

Comparative Example 4 Embodiment 7 was repeated without crown ether. HPLC analysis showed: c _NB = 1.40 M, c, p _C = trace, c _A = 0.08 M, c = _0PH = 0.02 M. Embodiment 8

Example 7 was repeated by using 0.15 mmol of dicyclohexano [8] krona-6 (55.3 mg) in place of the [18] crown-6. The reaction time was 2 hours. HPLC analysis showed: c _N e = 0.27 M, C | _PC = 1.06 M, c _A = 0.16 M, CDPH = 0,1OM.

Claims (7)

1. A process for the preparation of N-aryl carbamates by reacting nitroaromatics with alcohols and carbon monoxide under substantially anhydrous conditions in the presence of sulfur and / or sulfur compounds, characterized in that one uses catalyst systems containing as components sodium and / or potassium vanadates of the general formula M _k V, O _m · (H ₂ O) M = Na, K k, l, m, n = integer indices with k, l ^ 1, m § 3, η a O in combination with cyclic polyethers, preferably crown ethers. 2. The method according to claim 1, characterized in that as sodium and potassium vanadate sodium metavanadate (NaVO ₃ ), potassium metavanadate (KVO ₃ ), sodium orthovanadate (Na ₃ VO ₄ ), potassium orthovanadate (K ₃ VO ₄ ) and their hydrates and all intermediate forms, which correspond to the general formula, preferably the hydrate-anhydrous sodium and potassium vanadates are used. 3. The method according to claim 1, characterized in that as cyclic polyether crown ethers, neutral cyclic compounds having 5 to 10 oxygen atoms in the ring, between which each preferably 2 carbon atoms are used. 4. A process as claimed in claim 1, wherein the crown ethers [15] crown-5, benzo [15] crown-5, [18] crown-6, tetraphenyl- [18] crown-6, dibenzoyl, are used as cyclic polyethers. (18) crown-6, dicyclohexano (18j crown-6 and / or tribenzo (18) crown-6 are used. 5. The method according to claim 1, characterized in that are used as the nitroaromatic nitrobenzene, nitrotoluene, Nitrochlorbenzene, nitroxylenes, Nitrodichlorbenzene, Nitrochlortoluene, Nitrocumene or Nitromesitylen. 6. The method according to claim 1 to 4, characterized in that are used as nitroaromatics 2,4-Dinitrotoluen and / or 2,6-Dinitrotoluen. 7. The method according to claim 1 to 6, characterized in that are used as alcohols methanol, ethanol, n-propanol or iso-propanol.