US2527165A - Alkamine esters of 1-aryl-2, 5-dialkylpyrrole-3, 4-dicarboxylic acids - Google Patents

Description

Patented Oct. 24, 1950 ALKAMINE ESTERS OF 1- ARYL-2,5-DI- ALKYLPYB/ROLE 3,4 DICARBOXYLIC ACIDS Ruth A. Walker, Manhasset, N. Y., and Jackson P. Sickels, Coral Gables, Fla., assignors to American Gyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application February 4, 1948, Serial No. 6,336

11 Claims.

. This invention relates to mono and dialkamine esters of 1-aryl-2,5-dialkylpyrole-3,4-dicarboxylic in which alk stands for a lower alkyl radical and R stands for alkyl or all: C H N alk In the past, a number of diethyl esters of l-alkyl 2,5- dimethyl pyrrole- 3,4- dicarboxylic acids have been prepared and also a diethyl ester of l cyclohexyl 2,5 dimethylpyrrole 3,4 dicarboxylic acid. These esters were prepared by the standard method involving the Knorr synthesis. When it was attempted to prepare the diethyl ester of 1-aralkyl-l-2,5-diethylpyrrole-3,4- dicarboxylic acids the synthesis failed. According to the present invention, it has been found possible to prepare esters of l-aryl-2,5-dialkylpyrrole-3,4-dicarboxylic acids in which the alkyl groups may be not only methyl but also other alkyls having a larger number of carbon atoms such as ethyl, propyl, etc. These esters may be transformed into the corresponding 3,4-dialkamine esters which latter are all new compounds and are useful for a number of purposes. Thus, for example, the esters in the form of their addition salts with strong acids, such as hydrochlorides, exhibit local anesthetic power. The reason why it was found possible to prepare esters of 1-aryl-Z,5-dialkyl pyrrole-3,4-dicarboxylic acids in which the alkyl groups have more than one carbon atom whereas the same procedure failed in attempts to prepare corresponding l-aralkyl compounds has not been fully determined and the present invention is not intended to be limited to any particular theory with regard to this anomalous behavior.

The pyrrole dialkamine esters of the present invention may be prepared by catalysed alcoholysis of the corresponding pyrrole dialkyl esters with a dialkylaminoalkanol, using a small amount of an alkali metal alcoholate as the catalyst. However, poor yields are generally obtained by the ordinary alcoholysis procedure in which the esterand the dialkylaminoalkanol are heated together. Therefore, in order to get acceptable yields, it is necessary to employ a special procedure in which the reactants are permitted to stand at room temperature for a number of hours, for example, overnight, before heating.

Another method for preparing the pyrrole dialkamine esters, which is preferable in some respects, is to react the 1-aryl-2,5-dialkylpyrroie- 3,4-dicarboxylic acid with a dialkylaminoalkyl chloride.

The latter method is also employed to prepare the mixed pyrrole alkamine-alkyl esters. The anhydride of the 1-aryl-Z,5-dialkylpyrrole-3,4-dicarboxylic acid is reacted with an alkanol, thus forming the monocarbalkoxy-monocarboxylic pyrrole, which in turn is converted into the desired pyrrole mixed ester through its reaction with a dialkylaminoalkyl chloride.

The method involving the use of a dialkylaminoalkyl chloride produces the monoand dialkamine esters in the form of their hydrochlorides. When the dialkamine esters are desired in this form, but are prepared by the modified, catalyzed alcoholysis, it is, of course, necessary to react the free bases with a strong mineral acid, such as hydrochloric, in the conventional manner in order to form the addition salt.

The 1-aryl-2,5-dialkyl-3,4-dicarbalkoxy pyrroles, which are the starting materials for the synthesis of the pyrrole alkamine esters of the present invention, are prepared by the wellknown Knorr synthesis. This general reaction is described by Knorr, Berichte 18, 299 et seq. (1885), and involves the reaction of a diester of a diacylsuccinate with an aromatic amine. Some of the diacylsuccinates are known, such as the diacetosuccinates and the dipropionylsuccinates, but the other diacylsuccinates, such as the dibutyrylsuccinates, are new compounds. However, they may ,beprepared in the same manner as the known diacylsuccinates. Namely: an alkylmagnesium iodide is reacted with an alkyl cyanoacetate and the complex formed between the Grignard reagent and the cyanoester is hydrolysed, yielding the corresponding beta-keto ester. The beta-keto ester is then converted to the sodium enolate by reacting it with metallic sodium in a suitablesolvent. The addition of iodine to the resultant product causes the elimination of sodium iodide and the condensation of the enolate to the desired dialkyl diacylsuccinate.

While the above' described method of preparing the pyrrole dialkamine esters of the present invention is preferred, it should be understood that the invention is not limited thereto and in- 3 eludes the esters regardless of the method by which they are prepared.

The invention will be described in greater detail in conjunction with the following specific examples:

Example 1 The dihydrochloride of the di (beta-diethylaminoethyl) ester of 1-pheny1-2,S-diethylpyrrole- BA-dicarboxylic acid Ca. C

Ten parts of ethyl dipropionylsuccinate was dissolved in twenty-five parts of glacial acetic acid and was reacted at an elevated temperature with three and one-half parts of anilline, producing 1-phenyl-2,5-diethyl-3,4-dicarbethoxy pyrrole according to the usual Knorr synthesis. This product was drowned in water, filtered, and purified by crystallization from petroleum ether, (M. P. 61-62" 0.).

Nine parts of l-phenyl--2,5-diethyl-3,4dicarbethoxy pyrrole was added to a solution of twotenths part of sodium in thirty parts of betadiethylaminoethanol. This reaction mixture was allowed to stand at room temperature for fifteen hours and then the temperature was raised to 165 C. and was maintained at this level for eight hours (the reaction vessel having been fitted with an efiicient fractionating column). At the beginning of the heating, ethanol distilled off very rapidly until about one and one-half parts of ethanol had come over, but during the remainder of the time only a small amount of additional ethanol was removed.

After the heating was completed, the pressure i on the system was lowered to mm. and the excess beta-diethylaminoethanol was distilled ofi. The impure free base was converted to the hydrochloride by the following procedure: The oily residue was dissolved in ether and the resultant solution was washed with water and then thoroughly dried. A solution of dry hydrogen chloride in dry ether was slowly added, causing the formation of a sticky precipitate. This product was repeatedly triturated with dry ether and then further purified by reconversion to the free base, using a alcohol potassium hydroxide solution and extracting the base into dry ether. The oily hydrochloride was again precipitated by the slow addition of a solution of dry hydrogen chloride in dry ether to the ethereal solution of the base. The precipitate was then dissolved in chloroform and reprecipitated as a brown oil by the addition of ether. This oil solidified on standing and final purification was effected by crystallization from dry amyl alcohol, which resulted in a white, crystalline product (M. P. 1'77.5-178.5 C.) The di(beta-diethylaminoethyl) ester of 1-phenyl-2,5-diethylpyrrole-3,4- dicarboxylic acid is hygroscopic, very soluble in water and in methyl alcohol, .quite soluble in chloroform, and insoluble in ether.

The sodium used to catalyze the alcoholysis may be replaced by a corresponding amount of another alkali metal, such as potassium.

4 Example 2 The dihydrochloride of the di(beta-diethylaminoethyl) ester of 1-pheny1-2,5-diethylpyrrole- 3,4-dicarboxylic acid "can; CzH -HCI CzHs CzHs

1-phenyl-2,5-diethyl-3,4-dicarbethoxy pyrrole was saponified by heating it with alcoholic potassium hydroxide. A water solution of the potassium salt was then acidified with hydrochloric acid which precipitated the free acid as a white flocculent solid (decomp. 264265 0.). Ten

parts of the pyrrole dicarboxylic acid was then dissolved in fifty parts of isopropanol and eleven and three-tenths parts of beta-diethylaminoethyl chloride was added. This reaction mixture was refluxed for fourteen hours and was then cooled to about 0 C. The dimer which had precipitated in small amount was filtered off and seventy-five per cent of the isopropanol was evaporated under vacuum. Dry ether was then added to the residue, precipitating the oily hydrochloride which solidified upon standing at a low temperature. The product was purified by crystallization from a chloroform-ether mixture, yielding a compound with the same melting point as that P produced in Example 1.

Example 3 The diyhdrochloride of the di(gamma-diethylaminopropyl) ester of 1-phenyl-2,5-diethyl- 40 pyrrole-3,4-dicarboxylic acid Six parts of l-pheny1-2,5-diethylpyrrole-3,4-

dicarboxylic acid was added to fifty parts of dry isopropanol in a reaction vessel provided with an efficient reflux condenser. The suspension was heated to the point of reflux while being vigorously agitated and then nine and one-half parts of gamma-diethylaminopropyl chloride was gradually added. The temperature was then maintained at about 95 C. for eighteen hours.

After. the reaction was complete, the isopropanol was distilled off under vacuum until the reaction mixture had been reduced to about twentyfive per cent of its original volume. The residue was cooled to 0 C. and dry ether was slowly added, precipitating an oily solid from which the supernatant was decanted. This solid was then dissolved in chloroform and reprecipitated by the addition of dry ether. Final purification was accomplished by recrystallization from amyl alcohol. The diyhdrochloride of the di(gamma-diethylaminopropyl) ester of 1-phenyl-2,5-diethylpyrrole-3,4-dicarboxylic acid was isolated in the form of fine white crystals (M. P. 114-115 C.) and possesses properties which are similar to those of the corresponding di-beta-diethylaminoethyl ester described in Examples 1 and 2.

Example 4 47:0-0 O CaHs Twelve parts of 1-phenyl-2,5,-diethylpyrrole- 3,4-dicarboxylic acid and two hundred and fifty parts of acetic anhydride were heated together at 125 C. until the reaction was complete. Cooling and partial removal of the solvent under vacuum, caused the precipitation of the anhydride of 1 phenyl 2,5 diethylpyrrole 3,4 dicarboxylic acid as fine white needles, which could be purified by crystallization from ether. (M. P. 11254135 (3.).

Six parts of the anhydride described above and two and one-half parts of absolute ethyl alcohol were dissolved in fifty parts of dry pyridine and were heated at 20 C. for about one day. The pyridine was then removed under vacuum and two portions of absolute alcohol were successively added to the residue and distilled off. The crude l phenyl 2,5 diethyl- 3-carbethoxypyrrole-4-carboxylic acid was then purified by recrystallization from methanol (M. P. l44145 0.).

Three and nine-tenths parts of the monoester described above was suspended in fifty parts of dry isopropanol in a reaction vessel fitted with a reflux condenser and an eflicient stirrer. The mixture was heated to the point of reflux and then a solution of two and eight-tenths parts of gamma-diethyl-aminopropyl chloride in twentyfive parts of dry isopropanol was slowly added to the stirred suspension. The heating-(95 C.) and the stirring were continued for about eighteen hours, during which the pyrrole monoethyl ester went into solution.

After the reaction was complete, the volume of the mixture was reduced by about seventy-five percent by distilling off the isopropanol under vacuum. Dry ether was added to the cooled residual solution and a colorless oil separated immediately. which upon analysis proved to be the desired hydrochloride of the gamma(diethylaminopropyl) ester of 1 phenyl 2,5, diethyl 3- carbethoxypyrrole-4-carboxylic acid.

Example 5 The dihydrochloride of the di(beta diethylaminoethyl) ester of 1 p tolyl 2,5 diethylpyrrole-3,4-dicarboxylic acid CzHs boxylic acid was then suspended in fifty parts of dry isopropanol and was reacted with five and.

one-half parts of beta-diethylaminoethyl chlo-- ride in twenty-five parts of dry isopropanol, using the procedure described in Example 3.

After the reaction was complete, isopropanol was removed under vacuum until the volume of the reaction mixture had been reduced by half. The solution'was then cooled to 0 C. and the precipitated dimer was removed by filtration. The volume of solvent was further reduced under vacuum and dry ether was added to the residual solution until a light yellow oil separated out. The purification procedure described in Example 3 did not cause this oil to crystallize, even after long standing, to a degree which would permit the isolation of the product as a sharp melting solid. However, analysis proved that the oil was the desired dihydrochloride of the di-betadiethylaminoethyl ester of 1-p-tolyl-2,5-diethylpyrrole-3,4-dicarboxylic acid.

Example 6 V The dihydrochloride of the di(gamma-diethylaminopropyl) ester of l m tolyl 2,5 diethylpyrrole-3,4-dicarboxylic acid 3H3 o=c-o 0 o omcmcmN .1101

c=c coo OHzCHzCHzN .1101

The procedure of Example 5 was followed, substituting meta-toluidine for para-toluidine and gamma diethylaminopropyl chloride for betadiethylaminoethyl chloride. The dihydrochloride of the di(gamma-diethylaminopropy1) ester of 1- m tolyl 2,5 diethylpyrrole 3,4 dicarboxylic acidwas obtained as an oil after being purified as described in Example 3. This oil could be made to solidify upon trituration with dry acetone but the product was so hygroscopic that it could be maintained in the solid state only when kept under completely anhydrous conditions.

Example 7 The dihydrochloride of the di(beta diethylaminoethyl) ester of 1 p -,chlorophenyl 2,5- diethylpyrrole-3,4-dicarboxylic acid 0: -COOCHCHN .1101

1 p chlorophenyl 2,5 diethyl: 3,4 dicarbethoxy pyrrole (M. P. 83-84 C.) was prepared according to the procedure used in Example 5, substituting p-chloroaniline for p-toluidine in the Knorr synthesis. However, there was one change in the general procedure employed in Example 5. beta-diethylaminoethyl chloride had been added to the isopropanol solution of l-p-chlorophenyl- 2,5-diethylpyrrole-3,4 dicarboxylic acid (decomp. 244-245 (3.), the reaction mixture was allowed to stand at room temperature for a day before being refluxed for twenty hours. The dihydrochloride of the di(beta-diethylaminoethyl)ester of 1 p chlorophenyl 2,5 diethylpyrrole 3,4-

.HCl

CaHs

dicarboxylic acid was obtained as a white solid After the isopropanol solution of 7 (M. P. 180-182" C.), after purification and crystallization from amyl alcohol. The product is hygroscopic, very soluble in water and in methyl alcohol, quite soluble in chloroform, and insoluble in ether.

Example 8 The dihydrochloride of the di(gamma-diethylaminopropyl) ester of 1 phenyl 2,5 dipropylpyrrole-3,4-dicarboxylic acid (3: 1 C=CCOOCH:CH1OH1N Ethyl butyrylacetate was prepared by reacting eighty parts of ethyl cyanoacetate, dissolved in three hundred parts of dry ether, with two and one-half times the theoretical amount of npropylmagnesium iodide. The n-propylmagnesium iodide was prepared by the standard method for producing Grignard reagents, that is, the dry magnesium turnings were pretreated with iodine vapors and then reacted with n-propyl iodide in ether solution. After the Grignard reagent had been added to the ether solution of ethyl cyanoacetate, the reaction mixture was heated overnight at 70 C. Hydrolysis of the Grignard complex was accomplishedby pouring the viscous, fluorescent mixture onto cracked ice and carefully acidifying with sulfuric acid (1:1). The aqueous solution was then repeatedly extracted with ether and the combined ether extracts were neutralized with sodium carbonate, washed with water and dried. The ether was then evaporated and the residual ethyl butyrylacetate was distilled under vacuum.

Sixty-three parts of ethyl butyrylacetate dissolved in dry ether was slowly added to ten parts of sodium sand suspended in dry ether. A gummy mass was formed, which, after standing overnight at room temperature, was treated with fifty parts of iodine dissolved in a large volume of dry ether. When the reaction was complete, the iodine color remained in the reaction mixture and then the sodium iodide was filtered ofi. Decolorization of the ether solution with sodium carbonate and evaporation of the solvent left a mixture of the oily and the crystalline diethyl dibutyrylsuccinates. Solid diethyl dibutyrylsuccinate (M. P. 81-8l.5 C.) was obtained upon crystallization from ethanol, acetone, or ethyl acetate.

The diethyl dibutyrylsuccinate was then reacted with aniline in boiling glacial acetic acid, according to the standard conditions for the Knorr synthesis. The l-phenyl-2,5-dipropyl-3,4- dicarbethoxy pyrrole thus prepared was purified and crystallized from petroleum ether (M. P. '73.5-'74.5 C.).

This pyrrol dialkyl ester was converted to the dissolved in twenty-five parts of dry isopropanol was slowly added to the stirred suspension. After the addition of the chloride, the reaction mixture was heated at C. for about sixteen hours, until the reaction was substantially complete.

The volume of isopropanol was then reduced by about seventy-five percent by distilling off the solvent under vacuum. The addition of dry ether to the cooled, residual solution caused the precipitation of the white, oily hydrochloride. The dihydrochloride of the di-gamma-diethylaminopropyl ester of l phenyl 2,5 dipropylpyrrole-3,4-dicarboxylic acid was further purified and crystallized from amyl alcohol, yielding fine, white crystals (M. P. 2l'7-218 C.). This product is solubl in water, in methyl alcohol, and in chloroform, and is insoluble in ether.

Example 9 The dihychloride of the di(gamma-diethylaminopropyl) ester of 1-p-tolyl-2,5-dipropylpyrrole-3,4-dicarboxylic acid CzHl 3: COOCHzCHzCHzN .HCl C3117 C2115 1-p-toly1-2,5-dipropyl-3,4-dicarbethoxy pyrrole M. P. 93.5-94.5 C.) was prepared according to the procedure used in Example 8, substituting p-toluidine for aniline in the Knorr synthesis. However, there was one change in the general procedure employed in Example 8. After the isopropanol solution of gamma-diethylaminopropyl chloride had been added to the isopropanol solution of l-p-tolyl-2,5-dipropylpyrrole-3,4-dicarboxylic acid (decomp. l47-148 C.), the reaction mixture was allowed to stand at room temperature for twenty-four hours before being refluxed at 95 C. for eighteen hours. The dihydrochloride of the di(gamma-diethylaminopropyl) ester of l-p-tolyl-2,5-dipropylpyrrole-3,4- dicarboxylic acid, thus produced, did not crystallize as rapidly as the corresponding phenyl compound. However, analysis proved that the oil was the desired product. It is very hygroscopic, is soluble in alcohol and in chloroform, and is insoluble in ether.

Example 10 The dihydrochloride of the di(gamma-diethylaminopropyl) ester of 1-p-chloropheny1-2,5-dipropylpyrrole-3,4-dicarboxylic acid chloride was an oil which analysis proved to be the desired hydrochloride. The dihydrochloride of the di(gamma-diethylaminopropyl) ester of 1 p chlorophenyl -4.2',5 dipropylpyrrole 3,4- dicarboxylic acid is very hygroscopic and is soluble in alcohol and in chloroform, and insoluble in ether. 1 Example 11 The dihydrochloride of the di(beta-diethylaminoethyl) ester of1-phenyl-2,5-dimethylpyrrole-3,4-dicarboxylic acid 91 parts of the diethyl ester of 1-phenyl-2,5- dimethylpyrrole-3,4-dicarboxylic acid, (prepared by reacting a glacialacetic acid solution of symmetrical diethyl diacetosuccinate with a slight excess of aniline), was added to 455 parts of betadiethylaminoethanol in which 1 to 2 parts of metallic sodium was then dissolved. The reaction mixture was heated in a vessel provided with an efiicient fractionating column until it refluxed to the top of the column. The temperature rose to about 159. The refluxing was continued for many hours until the reaction was substantially complete at which time the excess beta-diethylaminoethanol was removed by vacuum distillation. The residue was dissolved in ether, washed with water, the ether solution dried and an ether solution of hydrogen chloride added. The hydrochloride which was precipitated was dissolved in water and saponified with potassium hydroxide to form the free base which was extracted with ether. After drying and removing the solvent, the free base remained as a residual oil which was distilled oil under 2 mm. pressure. The bulk of the material distilled over at 260-270 C.

The free base was re-dissolved in ether and the hydrochloride precipitated by adding an ether solution in hydrogen chloride. After recrystallization from butanol, the dihydrochloride of the di(beta-diethylaminoethyl) ester of 1- phenyl-2,5-dimethylpyrrole-3,4-dicarboxylic acid was obtained as a gray microcrystalline powder, melting at 185-188.5 C. (uncorr.)

Example 12 The product of Example 11 was produced by an alternate process. The diethyl ester of l-phenyl- 2,5-dimethylpyrrole-3,4-dicarboxylic acid was transformed into the corresponding potassium salt by means of alcoholic potassium hydroxide solution, separating the salt by filtration.

68 parts of the potassium salt were treated with 160 parts of thionyl chloride by heating to 50 C. with vigorous agitation for a number of hours until the salt had been transformed into the acid chloride. then distilled off in a low vacuum, the residue dissolved in benzene and filtered free from potassium chloride. To the benzene solution there was then added 100 parts of beta-diethylaminoethanol and the mixture heated for a number of hours at 50 C. until reaction was complete. Water and excess potassium hydroxide were then added and the product extracted with ethe and dried. A residual oil was obtained which had substantially the same boiling point as that produced in Example 11. On transformation into the hydrochloride by the procedure described in the same example and recrystallization from butanol, a product was obtained which was iden- The excess thionyl chloride was 10 tical with that produced by ample. v

In the examples, the dihydrochloride has been produced as an end' product since this is the form in which the products are useful aslocal anesthetics. In the examples describing theprocess of producing the esters by catalyzed alcoholysis, the free base is produced first. When the preferred method using the dialkylaminoalkyl chloride is followed, the dihydrochloride is produced in the first instance. These hydrochlo rides may be transformed into the free bases by neutralization with alkali in the conventional manner. The free bases are the form in which the esters affect the activity of rubber accelerators.

In the examples, the hydrochlorides of the esters have been described as the salts of strong mineral acids as this is the most commonly used mineral acid for formation of addition salts with amines; Other strong mineral acids such-as hydrobromic acid form the corresponding salts and are, of course, included in the broader aspects of the present invention.

In most of the examples the final step has been carried out in dry isopropanol. The nature of the alcohol does not exert any particular effect on the reaction. Any of the other lower aliphatic alcohols may be used, such as the butyl alcohols, normal propanol, etc. Isopropanol is preferred for one reason only, and that is that its boiling point is at about the temperature at which the reaction proceeds most smoothly. It can, therefore, be used as an accurate thermostat by operating under a reflux. This might be considered purely as a mechanical advantage of using isopropanol and the invention is in no sense limited to processes using this preferred alcohol as a solvent.

The most common dialkylaminoalkanols and chlorides are the diethylaminoalkanols and their chlorides. These have been described in the examples and are preferred. However, the alkyl group on the nitrogen is not a particularly critical part of the molecule as far as the preparation of the compounds is concerned and the corresponding dipropyl or dibutylaminoalkyl esters may be prepared, substituting beta dipropylor dibutylaminoethyl chloride for beta or gamma dipropylor dibutylaminopropyl chloride for the gamma diethylaminopropyl chloride. In its broader aspects the invention includes these other alkamine esters, but for most practical purposes the diethylaminoalkyl chlorides are more readily available and produce the most effective compounds. These are, therefore, preferred.

We claim:

1. Compounds selected from the group consisting of esters of l-monocyclic aryl-2,5-dialky the preceding ex+ pyrrole-3,4-dicarboxylic acids with dialkylaminoalkanols and the addition salts of the esters with strong acids.

2. Compounds selected from the group consisting of esters of l-monocyclic aryl-2,5-dialkylpyrrole-3,4-dicarboxylic acids with diethylaminoalkanols and the addition salts of the esters with strong acids.

3. Compounds selected from the group consisting of esters of l-rnonocyclic aryl-2,5-dialkylpyrrole-3/l-dicarboxylic acids with beta diethylaminoethanol and the addition salts of the esters with strong acids.

4. Compounds selected from the group consisting of esters of l-monocyclic aryl-2,5-dialkyl- '11 pyrrole-3,4-dicarboxylic acids with gamma diethylaminopropanoland the addition salts of the esters with strong acids.

5. Compounds according to claim 1 in which the alkyl groups on the 2 and 5 carbon atoms of the pyrrole ring are methyl.

6. Compounds according to claim 1 in which the alkyl groups on the 2 and 5 carbon atoms of the pyrrole ring are ethyl.

'7. Compounds according to claim 1 in which the alkyl groups on the 2 and 5 carbon atoms of the pyrrole ring are propyl.

8. Compounds according to claim 1 in which the l-ar'yl group is phenyl.

9. Compounds according to claim 1 in which the l-aryl group is tolyl.

10. Compounds according to claim 1 in which the l-aryl group is p-chlorophenyl.

11. A method of preparing dihydrohalides of esters of l-monocyclic aryl-2,5-dialkylpyrrole- 3,4-dicarboxy1ic acids with dialkylaminoalkanols 7 which comprises reacting the corresponding dialkylaminoalkyl halide with the corresponding 1- mononuclear aryl-2,5-dia1kylpyrrole-3,4-dicarboxylic acids.

RUTH A. WALKER. JACKSON P. SICKELS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS January 1946, vol. 18, pages 161 and 171.

Claims (1)

1. COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF ESTERS OF 1-MONOCYCLIC ARYL-2.5-DIALKYLPYRROLE-3,4-DICARBOXYLIC ACIDS WITH DIALKYLAMINOALKANOLS AND THE ADDITION SALTS OF THE ESTERS WITH STRONG ACIDS.