CS203020B2 - Method of preparing diphenyl-methan-monocarbamate and diphenyl-methan-dicarbamate and homologues of polymethylen-polyphenyl-carbamate and derivatives thereof - Google Patents

Description

The invention relates to a process for the preparation of aromatic carbamic acid esters - urethanes, in particular diphenylmethanedicarbamates and their higher homologues and derivatives, acid catalyzed by rearrangement of (alkoxycarbonyl) phenylaminomethylphenyl compounds, such as alkyl esters.

Polymeric aromatic carbamic acid esters - polyurethanes - such as diphenylmethanedicarbamates and related higher homologues of polymethylene polyphenylcarbamates are of increasing importance in particular for the preparation of commercially valuable diphenylmethane diisocyanates and mixtures of diisocyanates and polyisocyanates by decomposing such esters of polymeric aromatic carbamates. 3 919 279v

At present, there are no known successful operating methods for the direct preparation of esters of polymeric aromatic carbamic acids. The corresponding diphenylmethane diisocyanates and polyisocyanates, commercially available, are widely prepared by phosgenation of mixtures of diamines and polyamines obtained by condensation of aniline and formaldehyde with a catalytic amount of a mineral acid, for example, in a manner protected in U.S. Pat.

A process for preparing esters of polymeric aromatic carbamic acids-polyurethanes protected by US Patent No. 2,946,768 describes the condensation of arylcarbamic acid esters with carbonyl compounds in a dilute aqueous acidic condensation medium.

In this method, however, carbonyl compounds, such as formaldehyde, tend to react with the carbamate nitrogen atom to produce varying amounts of, for example, generally 15 to 50% by weight of undesired (alkoxycarbonyl) phenylaminomethylphenyl compounds in addition to the desired polyurethanes. tetramers 203020 etc. (alkoxycarbonyl) phenylaminomethylphenyl compounds (also referred to as N-benzyl compounds).

Attempts to prepare monoisocyanates or diisocyanates and polyisocyanates or otherwise utilize mixtures containing undesired N-benzyl compounds that cannot be converted to isocyanates by pyrolysis and polyurethanes encounter numerous problems, as the method of separating polyurethanes from N-benzyl impurities is unknown.

The invention relates to a process for the preparation of diphenylmethane monocarbamates and diphenylmethanedicarbamates and their higher molecular homologues, polymethylene polyphenylcarbamates, in which the (alkoxycarbonyl) phenylaminomethylphenyl compounds (N-benzyl compounds) are catalytically rearranged with a particularly acidic medium.

In particular, the invention is directed to a process for the preparation of carbamates by catalyzing the rearrangement of N-benzyl compounds obtained as by-products in addition to urethanes by condensation of lower alkyl esters of phenylcarbamic acid with carbonyl compounds such as formaldehyde in the presence of an aqueous acid solution. The mixture obtained in such a condensation process comprising diurethapes and polyurethanes, N-benzyl compounds, unreacted alkylphenylcarbamates and other by-products such as amines can be contacted at about 50-170 ° C with an acidic Lewis-containing medium. acid at a concentration of at least 0.5% by weight, calculated on the reaction mixture as a whole, while keeping the amount of water in the system to a minimum, to catalytically convert or rearrange N-benzyl compounds to the desired monourethanes, diurethanes and poly thany.

Alternatively, unreacted alkylphenylcarbamates can be removed from the mixture by, for example, vacuum distillation prior to this treatment. The process of the invention is also suitable for the acidic rearrangement of the N-benzyl compounds resulting from other methods of preparation, as discussed below.

The invention therefore relates to a process for the preparation of diphenylmethane monocarbamates and diphenylmethanedicarbamates and related polymethylene polyphenylcarbamates in high yield by conversion or rearrangement (alkoxycarbonyl) of phenylaminomethylphenyl compounds using Lewis acids as catalysts.

The invention also relates to a process for the acid-catalyzed conversion of (alkoxycarbonyl) phenylaminomethylphenyl compounds formed during the preparation of esters of dimeric and higher polymeric carbamic acids by condensation in dilute aqueous N-arylcarbamic acid esters, such as ethylphenylcarbamate, with carbonyl compounds. useful diurethane and polyurethane compounds.

The process for the preparation of diphenylmethane monocarbamates and diphenylmethanedicarbamates and homologues of polymethylene polyphenylcarbamate and their derivatives is thus characterized in that the (alkoxycarbonyl) phenylaminomethylphenyl compound of the formula I is characterized by:

COOR

where it means

X, Y, Z independently of one another are C 1 -C 3 alkyl, -NHCOOR, -CH 3 ArNHCOOR, -N (COOR) CH ₂ Ar, and wherein at least one of these is hydrogen,

R is C 1 -C 3 alkyl,

Ar phenyl substituted with optionally C 1 -C 3 alkyl and higher homologues of a compound of formula (I) contact with a catalytic amount of a Lewis acid having a concentration of at least 0 under anhydrous conditions at a temperature of 50 to 170 ° C, preferably under ambient pressure. 5% by weight of the reaction mixture as a whole with optional addition of an inert solvent and the desired carbamates are separated.

For example, diphenylmethane dicarbamate diethyl ester is prepared according to the following equations using 2 - [(ethoxycarbonylphenylaminomethyl) phenylcarbamic acid as the ethyl ester:

COOC 2 H 5 / Y-N-CH 7

NHCOOC2H5 acid

-—- Γ »solvent

2 - [(ethoxycarbonylphenylaminomethyl) phenylcarbamic acid ethyl ester

NHCOOC2H5

NHCOOC2H5 2,4-methylene-bis-phenylcarbamic acid diethyl ester, diphenylmethane-2,4'-dicarberate diethyl ester.

The acid-catalyzed rearrangement reaction may be carried out in any suitable reactor which is generally equipped with agitation means. In general, N-benzyl compounds are introduced into the reactor together with the Lewis acid catalyst and optionally the solvent, and the mixture is then maintained at the desired temperature for a suitable period of time.

The reaction may be carried out intermittently or continuously and the introduction of substances may be adjusted according to the apparatus used. The reaction products obtained are worked up by any conventional method, such as extraction of the acidic medium with water or neutralization with a base and separation of the resulting phases and distillation to remove the solvent used or filtration to separate the catalyst.

The (alkoxycarbonyl) phenylaminomethylphenyl compounds which can be converted or rearranged according to the process of the invention are characterized by the above general formula, which includes, for example, compounds of the following general formulas in which R is C 1 -C 3 alkyl:

COOR θ-N- CH ₂ · ethyl-N-benzylphenylcarbamate

COOR

COOR

N — i

CH;

NHCOOR alkyl ester of 2 - ((alkoxycarbonyl) phenyl (aminomethyl) phenylcarbamic acid) and 4 - [(alkoxycarbonyl) phenylaminomethyl] phenylcarbamic acid

COOR 5 --N - CH ₂ -

NHCOOR

CH ₂ NHCOR -fy-C dialkyl 4- (alkoxycarbonyl) phenylaminomethyl] -2,4'-methylene-bis-phenyl-carbamic acid

COOR

N-CH

COOR

J-CH2

NHCOOR

COOR COOR _<FA-N-CH2 - <FA-N-CH ₂ -X>

NHCOOR alkyl 4- {4- C (alkoxycarbonyl) phenylaminomethyl] phenyl (alkoxycarbonyl) eminomethyl} phenylcarbamic acid and 3- (4- (alkoxycarbonyl) phenylaminomethyl) phenyl (alkoxycarbonyl) aminomethyl) phenylcarbamic acid

NHCOOR

4- (4-f - (alkoxycarbonyl) phenylaminomethyl) phenyl (alkoxycarbonyl) aminomethyl] -2,4-methylene-bis-phenylcarbamic acid in the form of a dialkyl ester

These (alkoxycarbonyl) phenylaminomethylphenyl compounds, in particular the chemical formulas and names, are merely representative of other N-benzyl compounds, particularly the various isomers of these compounds, which are included in the above general formula and can be converted or rearranged to the desired carbamates, especially polycarbamates according to the invention.

In general, ethyl esters, i.e. compounds of formula I, wherein R is ethyl, obtained during the condensation of ethylphenylcarbamates (phenylurethane) with a carbonyl compound such as formaldehyde, useful for preparing diethyl esters of diphenylmethanedicarbamate and polymethylene polyphenylcarbamate which may decompose into polymer values. isocyanates as mentioned above.

As mentioned above, reaction products containing N-benzyl compounds formed as inseparable by-products during the condensation of alkyl esters of phenylcarbamic acid, such as ethylphenylcarbamate, with carboriyl compounds, such as formaldehyde, in the presence of a dilute aqueous acid solution, can be processed according to the process of the invention as such or after separation of the ethylphenylcarbamate unreacted starting material.

In addition, N-benzyl compounds can be used which can be prepared by other known methods. For example, N-phenylbenzylamine and an alkyl chloroformate, i.e., methyl chloroformate, ethyl chloroformate and propyl chloroformate, can be reacted to form the appropriate alkyl N-benzylphenylcarbamate. N-Phenyl-2-aminobenzylamine and N-phenyl-4-aminobenzylamine, prepared according to the method of GB Patent No. 1,177,557 (January 1970), can be reacted with an excess of alkyl chloroformate, such as ethyl chloroformate, to give the 2- and 4-C ethyl ester. (ethoxycarbonyl) phenylaminomethyl] phenylcarbamic acid.

£ alkyl 2- (alkoxycarbonyl) fenylaminomethylJfenylkarbamové acid and 4-C (L ^{and LT} oxycarbonyl) fenylaminomethylj f phenylcarbamic acid may also be prepared by reacting a substituted benzyl alcohol, for example ethyl ester benzylhydroxykarbamové (ethylfenylkarbamát-methylol-2) with an acid catalyst and ethylphenylcarbamate.

The Lewis catalyst which can be used as the catalyst in the process of the invention is, for example, tin tetrachloride, ferric chloride, aluminum chloride, pentafluorone antimony, and boron trifluoride.

The Lewis acid catalysts may be supported, for example graphite, and are used at a concentration of at least 0.5%, preferably 0.5 to 20% by weight of the reaction mixture as a whole.

Although the process according to the invention can be carried out in the absence of solvents, in particular at higher reaction temperatures, i.e. at 100 ° C and above, it can be used and generally used solvents or solvent mixtures which are stable and chemically inert to the components of the reaction system viscosity of mixtures of N-benzyl compounds in the form of dimers, trimers, tetramers, etc.

Suitable solvents which are used under substantially anhydrous conditions and generally in an amount of 0 to 50% by weight of the reaction mixture as a whole are, for example, nitrated and halogenated aromatic hydrocarbons having up to 2 carbon atoms, such as nitrobenzenes, nitrotoluenes, dichlorobenzene , dibromobenzene, alkanes and substituted alkanes of up to 16 carbon atoms such as n-pentane, isopentane, n-hexane, 2-methylpentane, n-heptane, 3,4-dimethylhexane, 2-methylhexane, 5-ethylpentane, cyclopentane, cyclohexane, methylcyclohexane, ethylcyclopentane, oyclooctane, chloroform, carbon tetrachloride, dichloroethane etc., lower aliphatic acids with up to 8 carbon atoms such as acetic acid, propionic acid etc. and lower aliphatic alcohols with up to 8 carbon atoms, for example methanol, ethanol, propanols , butanols.

Preferred solvents are nitrobenzene, nitrotoluene and dichlorobenzene.

Larger amounts of solvents may be used, but this is generally not necessary for the additional cost of recovery. Although a solvent mixture as mentioned above may be used, it is preferable to use a single solvent with respect to its regeneration.

As mentioned above, the process of the invention can be advantageously carried out by introducing the N-benzyl compounds contained in the condensate or other form together with the Lewis acid catalyst and solvent into a suitable reactor while maintaining a substantially anhydrous reaction medium and heating the mixture to the desired temperature.

The reaction proceeds at about 50-170 ° C. Generally, a temperature of 80 to 130 ° C is preferred to achieve a suitable reaction rate.

Heating and / or cooling means can be used inside and / or outside the reaction medium to maintain the temperature at the desired value.

The process of the invention is generally carried out at ambient pressure, although higher pressures may also be used at elevated temperature. Although it is possible to use a pressure lower than the ambient pressure, it has no meaning,

The reaction time generally depends on the use of the N-benzyl compound mixture or the condensate to be treated, the temperature and the type of acid catalyst used and varies depending on whether the operation is carried out continuously or continuously, generally from 2 minutes to several hours.

The following examples illustrate the process according to the invention but do not limit it in any way.

However, the process of the present invention is primarily directed to the preparation of diphenylmethane dicarbamate as the ethyl ester, and the ethyl ester of polymethylene polyphenylcarbamate by acid catalyzed conversion or conversion of ethyl (ethoxycarbonyl) phenylaminomethylphenylcarbamic acid, including higher homologues of trimers, etc .; as described above, the process of the invention is not limited to the preparation of such (ethoxycarbonyl) phenylaminomethylphenylcarbamic acid compounds, and it is clear to those skilled in the art that the process of the invention is widely applicable to other (alkoxycarbonyl) phenylaminomethylphenyl compounds such as methyl and propyl esters; higher homologues.

In the methods described in the following examples, the reactions were carried out in 300-mL three-neck glass reaction flasks equipped with a mechanical stirrer, reflux condenser and thermometer.

The reagents were charged to the flask and the flask was immersed in a constant temperature oil bath. At the end of the reaction time, water was added to the flask to cool the reaction mixture and the catalyst was removed and recovered by filtration. The conversion of the N-benzyl compounds, the product yield and the analysis are carried out by high-speed liquid chromatography.

He did

The test is carried out using 6 g of the ethylphenylcarbamate condensation reaction product with thioxioxane (98%) and 60% aqueous sulfuric acid. The condensate contains approximately 20% unreacted ethylphenylcarbamate, 44% diphenylmethane dicarbamate (2,4-isomer and 4,4'-isomer), 10% triurethane and higher molecular urethanes, 12% dimer of N-benzyl compound and 13% of trimers and higher N-benzyl homologs small amounts of undefined by-products.

The condensation product is dissolved in 6.0 g of nitrobenzene and contacted with 0.70 g of anhydrous ferric chloride for 30 minutes at 100 ° C. The reaction product is cooled with water and the ferric chloride is separated from the organic product by washing with water. HPLC revealed 100% rearrangement of the N-benzyl compound.

Example 2

Further tests were carried out as described in Example 1 using 6.0 g of nitrobenzene as solvent in each test. The reaction was carried out under different reaction conditions and using different Lewis catalysts.

The catalyst is filtered off from the reacted mixture or extracted with water by washing the reaction mixture and the reaction product is analyzed by high-speed liquid chromatography for a rearrangement of the N-benzyl compound. The results are shown in Table I.

Table I

Exam Acid catalyst Temperature Reaction time Percentage converted. . number G oc min N-benzyl compounds 1 ferric chloride - (0.67 g) 80 30 60 2 ferric chloride ^) (0.09 g) 150 15 Dec 50 3 aluminum chloride <1.20 g) 120 60 59 4 (2) antimony pentafluoride (27% antimony) on graphite (0.7 g) 120 60  100 ALIGN! 5 (2) antimony pentafluoride (27% antimony) on graphite (0.11 (g) 120 30 85 6 boron trifluoride etherate ^ (48% boron trifluoride) (2.3 g) 120 60 '94 7 aluminum chloride ⁽²⁾ (7% aluminum) on graphite (0.8 g) 120 60 57

Lewis acid filtered and washed with water (2) Lewis acid filtered for regeneration washed with water for extraction (4) total 100% conversion of dimers, trimers and tetramers etc.

Claims (9)

SUBJECT OF THE INVENTION V. A process for the preparation of diphenylmethane monocarbamate and diphenylmethane dicarbamate and homologues of polymethylene polyphenylcarbamate and derivatives thereof, characterized in that the (alkoxycarbonyl) phenylaminomethylphenyl compound of the formula I is: COOR (I) where is X, Y, Z are independently C1-C3 alkyl, -NHCOOR, -CHgArNHCOOR, -N / COOR / CHgAr, and at least one of which is hydrogen, R is C 1 -C 3 alkyl, Ar is optionally substituted C 1 -C 3 alkyl, and the higher homologues of a compound of formula I are contacted with a catalytic amount of Lewis acid at a concentration of 50 to 170 ° C under anhydrous conditions. at least 0.5% by weight of the reaction mixture as a whole, optionally adding an inert solvent and separating the desired carbamates. 2. A process according to claim 1 wherein the reaction is carried out in the presence of a solvent selected from the group consisting of saturated and halogenated hydrocarbons having up to 12 carbon atoms, alkanes, substituted alkanes having up to 16 carbon atoms, aliphatic acids having up to 8 carbon atoms, and aliphatic alcohols having up to 8 carbon atoms. Process according to Claim 1, characterized in that nitrobenzene, nitrotoluene or dichlorobenzene, in particular nitrobenzene, is used as solvent. 4. Process according to claim 1 or 2, characterized in that the reaction is carried out at a temperature of 80 to 30 ° C. 5. The process of claim 1 wherein the Lewis acid is tin tetrachloride, ferric chloride, aluminum chloride, antimony pentafluoride or boron trifluoride. 6. A process as claimed in claim 1, wherein the Lewis acid is used in a concentration of 0.5 to 20% by weight of the reaction mixture as a whole. 7. A process as claimed in claim 1, wherein the Lewis acid catalyst is supported. 8. The process of claim 7, wherein the Lewis acid is used on the graphite as the carrier. 9. A process as claimed in any one of claims 1 to 8 for the preparation of diethyl ester of diphenylmethanedicarbamate, characterized in that the 2-E (ethoxycarbonyl) phenylaminomethyl] phenylcarbamic acid ethyl ester or 4-C (ethoxycarbonyl) phenyl] aminomethyl] phenylcarbamic acid ethylcarbonyl the compound in the presence of an aqueous dilute acid solution, at ambient pressure, at a temperature of 80 to 130 ° C, in the presence of 0.5 to 20% by weight of antimony pentafluoride, based on the weight of the reaction mixture.