DE2160111C3 - Process for the preparation of an N-substituted carbamate - Google Patents

Description

^ The invention is a method for Preparation of an N-substituted carbamate by reacting an alkyl, aryl or alkylaryl ester of Carbonic acid with a primary or secondary amine at temperatures of about 20 to 250 ° C

Carbamates can, for example, by reacting isocyanates with alcohols or by reacting a Amine and an alcohol can be produced with phosgene. However, since carbamates turn into isocyanates can be transferred, for example under the action of heat, and therefore to create connections are used, which we used in the manufacture of polyurethanes. can is a Process desirable that enables the preparation of carbamates in a synthetic way for the you don't need isocyanate as an intermediate dangerous and toxic phosgene manage.

From FR-PS 1096 204 a process for the implementation of urethane derivatives of glycols is through Reacting cyclic carbonates of glycols with primary or secondary amines known

According to DK-PS 1 04230 phenylhydroxyalkylcarbamic acid esters are prepared by using a primary or secondary amine reacts with a phenyihydroxyalkyl chlorocarbonate or carbonic acid ester Establishing the latter connection takes place by converting Styrdgiykol or in the Side chain of aücyisubsutuierter styrene glycols with Phos-4s gea

Processes for the production of N-substituted carbamates do not go out of the two literstursteüen emerged.

From Houben-Weyl, Methods of Organizational Chemistry, Vol. 8 (1952), p. 139, the implementation neutral carbonic acid ester, for example diethyic

Formed with ammonia or füjafninen hfticniplcwpJcp Ethylenediamines, known In the first case one obtains unsubstituted urethanes and in the second case correspondingly substituted urethanes. However, considerable amounts of by-products are always formed ; -. ^ In Journal of American Chemical Society, Vol. 78 '$ 4 (1956), p. 4360, left column, previous paragraph, a, ^ reaction of methylamine with dimethyl carbonate in; ^ low temperature described. The so-called crude methyl N-methyl carbamate obtained in this way, however, was never isolated and analyzed, but was converted in one go ^: with sodium methylate as a catalyst to give the desired trimethyl isocyanurate

None of the above «procedures are possible the production of N-substituted carbamates, especially N-substituted alkyl carhamates or alkyl-N-arvI-

55

65 carbamate, in high selectivity and yield. task the invention is therefore to provide an improved method for making such compounds.

It has now been found that this task at Process of the type mentioned at the outset can be solved by starting the reaction in the presence of one a compound of a metal from HL to V !!!. group of the periodic table of the existing Lewis acid catalyst

These Lewis acids apparently have a special catalyzing effect for this reaction, and it it has been found that they particularly promote the reaction between an aromatic amine and an alkyl carbonate catalyze effectively.

Good yields of carbamates are achieved according to the claimed process, but also substituted ureas as by-products of the process generated, which apparently result from further reaction of the amine with the carbamate. These substituted ureas are valuable products in themselves can be done by known measures, e.g. by Treatment with alcohols to be converted into the relevant carbamates. Alternatively, such substituted ureas by suitable measures, for example by heating, according to known Methods converted into isocyanates.

The alkyl, aryl or alkylaryl esters of carbonic acid can be an alkyl radical with up to 12 carbon atoms, preferably a lower alkyl radical, d. H. with up to 6 carbon atoms, or one Aryl radical with up to 10 carbon atoms, e.g. B. contain a phenyl radical, naphthyl radical or alkyl-substituted phenyl radical. Typical carbonates used for the Purposes according to the invention are used, for example

Dimethyl carbonate diethyl carbonate Dipropyl carbonate, dibutyl carbonate, Dioctyl carbonate, methyl ethyl carbonate, Methyl butyl carbonate, diphenyl carbonate, Methyl phenyl carbonate and ditolyl carbonate

These carbonates can be easily produced by various known methods.

The synthesis of symmetrical dialkyl carbonates is described in US Pat. No. 3,227,740, Methods for the preparation of carbonates with various alkyl radicals are explained in US Pat. No. 3,227,741, and Methods of making diaryic carbonates are disclosed in US Pat the US-PS 32 34 263 indicated.

In this formula, compounds of the general formula R — NH — R 'are used as offices R means an organic structure, e.g. B. an alkyl group, an aryl group or an aralkyl group. the Alkyl groups can contain up to 32 carbon atoms and preferably contain up to 12 carbon atoms, and the aryl or aralkyl groups resulting from a benzene or naphthalene ring substituted by alkyl radicals or can consist of aryl or aralkyl radicals, preferably contain up to IS carbon atoms. the The alkyl group can be an acyclic radical with a straight-chain or branched structure or an alicyclic radical Be rest. The radical R can contain an inserted heteroatom, for example O or S, and one or have several primary or secondary amino groups. In the formula given above, means R 'is preferably hydrogen, but like R can be Be alkyl, aryl or aralkyl radical and in a given compound the same meaning as R or have a different meaning than R. If R and

R 'are alkyl groups, they can be taken together may be linked to the nitrogen atom to which they are attached to form a heterocyclic ring. Around R 'can also be replaced by non-interfering groups, e.g. alkoxy groups, halogen atoms and amido groups, be substituted. One class of amines of the formula given above is formed by diamines of the formula H2N — A— NH2, in which A is an organic radical corresponding to R, e.g. an alkylene, arylene or Aralkylene radical, which may contain inserted heteroatoms, means examples of typical amines that are in the method according to the invention can be used

Methylamine, n-butylamine, octylamine,

Tetramethylenediamine, hexamethylenediamine, dibutylamine, aniline,

Toluidine (o-, m-, or p-), 2,4-xyIidine,

3,4-xylidine, 24-xylidine, 4-ethylaniline,

3-propylaniline, 1,3-di? ·! inobenzene,

2,4-diaminotoluene, 4,4'-diamino-diphenylmethane,

p-chloraniiine, _6-diaminotoluene,

4,4'-diamino-diphenyl,

2,4,4'-triaminodiphenyl ether,

2,6-diaminonaphthalene, 1 ^ -diamino-2-methylpentane,

Benzylamine, phenylethylamine, piperidine,

Morpholine, piperazine, glycine, phenylalanine,

Phenoxyethylamine, / \ J10xyethylamine,

2-methoxy-5-chloroaniline, 2-aminoethyl ether,

2-aminoethyl sulfide, cyclohexylania
The preferred amino groups are any aromatic amines and the preferred carbonates are the lower alkyl carbonates, especially diethyl carbonate

The catalysts used in the process according to the invention are those Lewis acids which consist of compounds of metals from groups HI to VIII of the periodic table (Handbook of Chemistry, 10th edition, NA Lange, McGraw-Hill Book Company, Inc. [1961], p. 54). There are known compounds and for example ^; "Physical Organic Chemistry" by Jack H i η e (1962, McGraw-Hill Company, New York) and in "Friedel-Crafts & Related Reactions" by George A. 01 ah, Vol. I, (1963, Interscience Publishers, New York) explains and defines some examples of Lewis acids

Antimony trichloride, aluminum chloride,

Antimony fluoride, Fei ricWorid,

Antimony pentachloride, niobium pentachloride, tantaltetrachlorii titanium tetrachloride,

Boron trifluoride. Antimony pentafluoride,

Stannifluerid, aluminum bromifl,

ThaHium trichloride, uranyl nitrate,

Uranium tetrachloride, uranium oxides, e.g. B. UO2.

Further examples are given in the publication "Friedel-Crafts and Related Reactions", which deals mainly with Lewis acids of the salt type. Preference is given to metal compounds of groups V and VI and, in particular, of metals with atomic weights above 120. In general, the preferred Lewis acids are salts, e.g. B. Halides, and the Lewis acids, which have proven to be particularly useful and advantageous, are compounds of uranium, including uranyl compounds, ie compounds containing the UO2 ⁺⁺ radical, especially the salts, for example uranium tetrachloride, uranyl chloride, uranyl nitrate and uranyl acetate .

If the amine and / or carbonate is normally solid at room temperature, then use of a solvent is expedient. Suitable solvents are the customary inert organic solvents Compounds used as solvents in organic syntheses, e.g. B. aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane, octane and Dodecane, halogenated aliphatic hydrocarbons such as 1,1,2-trichloroethane and 1,2,2-trifluoroethane, halogenated aromatic hydrocarbons such as monochlorobenzene, dichlorobenzene and trichlorobenzene, ethers such as Dibutyl ether, dioxane, ethylene glycol diisoamyl ether and diethylene glycol diethyl ether and similar inert organic Solvent. If at least one of the reactants is normally at room temperature is liquid, it is generally not necessary to use a solvent as the liquid Reactant can usually serve as a solvent for the solid reactant, though an inert organic solvent can be used if it is found that the Handling of the reaction medium in question is facilitated.

The reaction? \> Ύ "" Hem carbonate and the amine takes place at moderately erh> hten temperatures, eg., Temperatures of 20 to 150 ⁰ C, smooth, so there is no need for the application of high temperatures, there is preferably a temperature in the range from 30 to 110 ^° C. It should be noted, however, that higher temperatures can be used if desired, for example temperatures up to 250 ^° C. and above, but the temperatures used should be below the temperatures at which decomposition of a reactant or reaction product takes place Pressure is not critical to the process and the reaction can usually be carried out at atmospheric pressure. However, if desired, in cases where one or more of the reactants are relatively low boiling substances, pressures greater than two atmospheres can be used but usually not required.

The reaction can be carried out with stoichiometric amounts of the reactants, preferably however, one of the reactants, especially the carbonate, becomes irr. Excess applied the The amount of the excess reactant may vary, but it is preferred that it be excess to at most 50 moles and preferably 15 moles of the reactant used in excess per mole of the other respondent limited

Three quantities of the acid catalyst can vary, and even very small amounts will effectively catalyze the reaction In general however, it is appropriate to use at least about 0.005 mole percent Lewis acid, based on the amount of Reactant in a stoichiometric amount, i.e. H. is not present in excess. Since it is in It is generally preferred that the carbonate be present in excess based on the amount of catalyst generally based on the amount of amine introduced into the system. The maximum amount of Lewis acid used is generally determined by economic factors. Usually the application offers amounts of more than 25 mole percent are of no particular advantage. The optimal amount of catalyst depends on the reaction conditions and on the

each Lewis acid used, but it is usually advantageous to 0.1 to 10 mole percent of the Lewis acid and preferably to use 0.5 to 10%.

The inventive reaction between the amine and the carbonate in the presence of Lewis acid . Can be carried out in any convenient reaction vessel will. If excess pressures are to be used, the vessel £ 3 is expediently constructed so that it withstands the maximum pressure to be applied. The implementation is usually carried out so that dL both ι ο Reactant and the cata οι in the Reaction vessel are introduced * ... the

Reaction mixture during a r- ^ EIT

duration to the desired response ■■. ' . · Ϊγ is heated. The response time can; .it «, iei. -side area, e.g. B. 0.1 to 48 hours, fluctuate and is not a critical factor of the process according to the invention, although long reaction times can promote the formation of the substituted urea at the expense of the carbamate. Usually, reaction times of more than one sense are more preferred, but reaction times of over 24 hours are generally of no advantage with regard to carbamate formation. The reaction can be carried out batchwise or continuously. The process according to the invention is suitable for continuous implementation due to the fact that all reactants can be introduced into the system together in the appropriate proportions.

The reaction according to the invention between the carbonate and the amine leads to the simultaneous release of the alcohol which corresponds to the carbonate ester group. Since the reaction is generally inhibited by the presence of this alcohol, it is preferred to remove the released alcohol from the system. This can best be done by equipping the reaction vessel with a rectifying column and carrying out the reaction at the reflux temperature of the reaction mixture. In this way, the alcohol can be removed from the head continuously or intermittently as required. Alternatively, the reaction can first be carried out below the reflux temperature and then the mixture can be heated to the reflux temperature if the alcohol is to be removed and the reaction is to be accelerated. As already mentioned, the process described above enables the production of considerable amounts of carbamates from aromatic or aliphatic amines and aromatic or aliphatic carbonates, but different amounts of the _sn j _S p _rcc u _c _ _; i _c _ ".u ^ jjj ^ jj. Ureas "ebüdei.

At the same time, N-substituted amines are in different Generated quantities. It has been found that between the various Lewis acids that are used for the purposes according to the invention are used in terms of the ratio of carbamates to substituted Urea and N-substituted amines generated when they are used have certain differences exist. The uranium and uranyl salts have each other in terms of favorable ratios of carbamates By-products found to be particularly beneficial. It was also found that excess amine the formation of substituted ureas favors, while excess periods o the production of such By-products suppressed.

The following examples illustrate the process of Invention explained in more detail

example 1

A 500 ml flask equipped with a 20-bottom Oldershaw distillation column is filled with 180 g (2 mol) of dimethyl carbonate, 37.2 g (0.4 mol) of aniline and 11.4 g (0.05 mol) of antimony trichloride loaded. The solution is heated to the reflux temperature through the column and when enough alcohol has formed so that the head temperature falls to 85 ⁰ C, a mixture of dimethyl carbonate and methanol is removed overhead The flask remains at about 100 ^° C., the reaction is ended, the reaction solution is cooled, and 13.3 g of solid diphenylurea are removed by filtration. Over 56% of the aniline responded, and at Anai. °. of the filtrate is found to consist mainly of methyl N-phenylcarbamate together with a small amount of N-methylaniline easily separated into its components by fractional distillation. The residue is recrystallized from hexane and filtered hot, yielding the pure methyl N-phenyl carbamate. The ratio of carbamate to substituted anine is about 5: 1.

Example 2

Following the procedure and using the apparatus of Example 1, the plunger weighs 180 grams Dimethyl carbonate, 37.2 g aniline and 5.02 g uranyl nitrate charged The solution is brought to reflux temperature, and after the head temperature has fallen to 78 ° C, a mixture of dimethyl carbonate and methanol is removed in a total amount of 68.1 g. After a period of 1.25 hours, during which the temperature in the flask remains at about 100 ° C, the The reaction is complete and the solid diphenylurea (1.2 g) is filtered off. The analysis of the product shows 11.83 g of methyl N-phenyicarbamate and 6.3 g of N-methyl aniline.

Example 3

Following the procedure of Example 1, 1.46 parts by weight of n-butylamine are 1.80 parts by weight Dimethyl carbonate in the presence of 0.25 parts by weight Uranyl nitrate reacted as a catalyst for 31.5 hours at about 80.degree. C. It is found that the product is 2.53 Share methyl N-butyl carbamate and small amounts Contains by-products

Example 4

Following the general procedure of Example 1 using hexamethylenediamine Instead of aniline a'j carbamate product di-methoxycarbonylhexamethylenediamine,

CH3OOCNHCH2CH2CH2CH2CH2CH2NHCOOCH3

receive.

Example 5

When 4.28 g of diphenyl carbonate are reacted with 1.86 g of aniline in the presence of 0.001 mole of antimony trichloride at 8O ⁰ C, 36% of the diphenyl carbonate react in 3.5 hours. If the antimony trichloride is replaced by 0.0005 mol of uranyl nitrate, 29% of the diphenyl carbonate are converted in the same time.

Phenyl-N-phenylcarbamate is used as the carbonate product in every case receive. If the reaction is repeated at the same temperature without a catalyst, only 8% of the diphenyl carbonate react in 3.5 hours.

Example 6

If the general procedure of Example 2 was carried out with 0.05 moles of uranyl nitrate and 0.4 moles of aniline, but with Diethyl carbonate (2 mol) instead of dimethyl carbonate repeated and the reaction is carried out for 1 hour at 85 ° C., ethyl N-phenylcarbamate is used as the carbamate product receive.

Example 7

The general procedure of Example 1 is repeated except that the aniline is through 2,4-Toluylenediamine is replaced. The product is dimethoxycarbonyl-2,4-tolylenediamine

NHCOOCH ₃

NHCOOCH,

together with monomethoxycarbonyl ^ -tolylenediamine and N-methylated diamines are obtained as by-products.

Example 8

Following the general procedure of Example 2, 37.2 g of aniline and 18Og of dimethyl carbonate are in The presence of 0.01 mol of uranyl chloride reacted for 3 hours at lore There are 213 g of methyl N-phenylcarbamate, 33 g of N-methylaniine and 1.1 g of diphenyl urea generated

Example 9

The procedure of Example 8 is repeated with the exception that the reaction is i2.7 hours is carried out at 96 ° C. There are 20.4 g of methyl N-phenylcarbamate, 4.6 g of N-methylaniline and 1.6 g of diphenylurea produced

Example 10

Following the general procedure of Example 2, 510 g of aniline and 535 g of dimethyl carbonate in the presence of 56 g are UCU 28.4 hours at 80 ⁰ C converted the product contains 248 g of methyl N-phenylcarbamate, 15.6 g of N-methylaniline and a small amount of diphenylurea.

Example 11

When following the procedure of Example 1 with cyclohexylamine is repeated instead of aniline, methyl N-cyclohexylcarbamate is obtained as the carbamate product.

Example 12

Following the general procedure of Example 1 using t-aminonaphthalene Instead of aniline as a carbamate product, methyl N-naphthyl carbamate receive.

Example 13

Following the procedure of Example 1, 3-chloroaniline is used instead of unsubstituted aniline as the carbamate product
receive.

^ 8

Methyl N- {m-chlorophenyl) carbanate

Example 14

To demonstrate the effect of uranyl acetate 'as. The catalyst is 510 g of aniline and 535 g of Dinustnyjv carbonate reacted for 26.75 hours at 80 ° C in the presence of 20 g of uranyl acetate The ratio of the product -, Methyl-N-phenylcarbamate to which as a by-product * substituted aniline formed is 3.0Vl.

If attempts v / IRAE, the reaction between dimethyl carbonate and aniline in a molar ratio 1: perform 1 at 80 ° C in the absence of a Lewis acid, no carbamate and no substituted aniline are produced when an excess tn dimethyl carbonate is used even after 240 hours, the same received negative results. If the temperature is increased to 150 ^° C., only trace amounts of these compounds are obtained even after several hours.

Test report

To determine the influence of Lewis acids to the reaction of alkyl carbonates with amines equal volumes (about equimolar amounts) of dimethyl carbonate uhd aniline in the presence of small amounts of various Lewis acids on 8O ⁰ C heated After the reaction dac reaction mixture is its content of N-phenylmethylcarbamate and N with respect to -Phenylaniline investigated. The results obtained are summarized in the following table. The selectivity of the reaction in favor of the carbamate is shown in the right-hand column of this table.

SbCIi 0.044

., SbCt ₃ 0.022

UO2 (NOj) 2 0.015
AICIj 0.075

SbFa 0.028

FCh 0.062

0.033
0.036
0.028
0.028
0.026
0.028

Lewis Kataly Tempe time Gpwichls- acid sator rature ratio made of carbamate and substitute ated aniline (h / tol) Γ C) (Hours)

SbFa
FeCh
SbCh
NbCh
UO2
UOj
UCU
. ThCU

80
80
80
80
80
80
80
80
80
80
80
80

18th

24

23.5

18th

24

18th

18th

233

243

25.2

28.4

21.9

4.8: 1

43: 1

4.0: 1

2.7: 1

23: 1

2.2: 1

2.1: 1

135: 1

6: 1

9: 1

13: 1

In another attempt, the same volumes are used Dimethyl carbonate and starter in turn on SCFC heated, but in this case without a catalyst, self after 240 hours of heating can be im No carbamate or substituted aniline found in the reaction mixture.

The above attempt is in the absence of -, one ;, Catalyst repeated, but with one. Volume ratio of dimethyl carbonate to aniline of 5: 1 works in the reaction mixture after 91 Neither carbamate nocti determine substituted aniline.

609647/209

In a further experiment without a catalyst, dimethyl carbonate and aniline are heated in a volume ratio of 3: 1 to 15U ⁰ C, and after 4.5 hours of reaction, traces of a reaction product can be found in the reaction mixture in which the amount of methyl aniline is many times greater is than the amount of N-phenylmethyl carbamate

The above verse is used with a molar ratio of Dimethyl carbonate to aniline of 2: 1 and at a temperature of 200 ° C repeated after 2 hours Implementation time can only be very small amounts determine a reaction product. The analysis shows that the main product is N-methylaniline, the ratio of N-methyl aniline and N-phenylmethyl carbamate being about 50: 1

The above experiments clearly show that the presence of Lewis acids at a relatively low temperature increases leads to a reaction which, with respect to the carbamate extremely selective

The use of a Lewis acid as a catalyst, as shown above, is particularly beneficial the preparation of a carbamate having at least one aryl group, but result using this catalyst also in the production of other carbamates compared to the known procedure special advantages; These advantages can be seen from a comparison of Example 3 with the information in FIG already mentioned literature Journal of American Chemical Society, Vol. 78, 1956, p. 4360. Example 3 shows the production of methyl N-butyl carbamate by reacting N-butylamine with dimethyl carbonate and thus an N-alkyl carbamate, which with the in above

ίο Methyl-N-methylcarbamate mentioned as a crude product is extremely closely related due to the literature higher alkyl group, with which one has to do it in the reaction according to Example 3, one would expect this implementation to be more difficult should. As can be calculated from Example 3, one obtains after this procedure, however, a conversion of 96 ^%, while the in J. Am. Chem. Soc, loc. Cit. The reaction described in itself, which proceeds more easily, only gives a yield of 75% .This shows that that the inventive use of a Lewis acid catalyst also applies to the production of Alkyl-N-alkyl carbamates generally have beneficial effects.

"Co j · ■ -

Claims (1)

Claim: , Process for the preparation of an N-substituted carbamate by reacting an alkyl, aryl or alkylaryl ester of carbonic acid with a primary or secondary amine at temperatures of about 20 to 250 ⁰ C, characterized in that the reaction is carried out in the presence of a compound a metal of III. to VIII, group of the periodic table of the existing Lewis acid catalyst