MXPA96004280A - Process for the preparation of succinilsuccinatos dialquili - Google Patents

Abstract

Dialkyl succinylsuccinates are prepared in a pure form and with a high yield, by the reaction of an alkali metal alcoholate with an excess of dialkyl succinate under anhydrous conditions, followed by isolation of the di (alkali metal) salt of the dialkyl succinylsuccinate, and then the neutralization of the conacid salt. The resulting dialkyl succinylsuccinate is isolated or used, without isolation, as an intermediate in the production of quinacridone pigments. The disclosed process provides high yields and a reduced organic waste, comparing with the known processes

Description

PROCESS FOR THE PREPARATION OF SUCCINILSUCCINATOS DI LQUILICOS The present invention relates to the preparation of dialkyl succinylsuccinates in a pure form and with a high yield, by the reaction of an alkali metal alcohol slag with an excess of dialkyl succinate under anhydrous conditions, to isolate the solid di (alkali metal) salt of the dialkylic succinylsuccinate under anhydrous conditions, and then neutralizing the salt with acid to produce the free succinyl lysuccinate dialkyl ester; to a salt complex of di (alkali metal) succinylsuccinate dialkyl-succinate dialkyl ester; and to a process for the preparation of quinacridones from the present dialkyl succinylsuccinates. The use of anhydrous conditions during the reaction and the isolation allows the excess of dialkyl succinate to be easily regenerated to be reused in the next reaction. The preparation of dialkyl succinylsuccinates, which are also known as 2,5-dihydroxy-3,6-dialkyl dihydroterephthalates or cyclohexan-1, dialdenedione-2,5-dione dicarboxylates, is known in the art by the reaction of a succinate of dialkyl with an alkali metal or with an alkali metal alcoholate in the presence or absence of one or more cosolvents or diluents, one of which is usually an alcohol. It is preferred to use an alkali metal alcoholate because of the fire and explosion hazards associated with the handling of alkali metals. The most known processes using an alkali metal alcoholate react the dialkyl succinate cnn more than the theoretical amount of the alkali metal alcoholate. For example, U.S. Patent No. 4,435,589 describes a process wherein dimethyl succinate is added to a methanolic solution containing from 120 to 180 percent of the theoretical weight of sodium methylate, to produce the disodium salt of succinylsuccinate of dimethyl and succinylsuccinate dimethyl by subsequent acidification. It is also known to use an excess of the dialkyl succinate reagent. For example, European Patent EP-A-166,214 describes a process in which a solution of 5 to 45 percent of alkali metal alcoholate in alcohol is added to an excess of dialkyl succinate. After distilling the alcohol, the dialkyl succinylsuccinate alkali metal salt is neutralized, without isolation, to produce the dialkylic succinylsuccinate by mixing an aqueous acid with the mixture containing the excess of dialkyl succinate and the alkali metal salt of dialkylic succinylsuccinate. The disclosure indicates that excess dialkyl succinate can be recovered and reused. However, since excess dialkyl succinate is combined with the aqueous acid prior to recovery, it is necessary to separate the aqueous and organic phases. Losses in yield can occur due to the solubility of the dialkyl succinylsuccinate in the dialkyl succinate, and in the recovery of dialkyl succinate from aqueous acidic media. The present invention relates to a novel process for the preparation of a high purity dialkyl succinylsuccinate with a high yield. The high yield is based on both the dialkyl succinate and the alkali metal alcoholate. An object of the present invention is a process for the preparation of a dialkylic succinylsuccinate, which comprises the steps of: (a) preparing a di (alkali metal) salt of dialkyl succinylsuccinate by reaction of a mixture consisting essentially of a alkali metal alcoholate, an aliphatic alcohol, and an excess of a liquid dialkyl succipate under anhydrous conditions at an elevated temperature; (b) removing the aliphatic alcohol from the reaction mixture; (c) separating the di (alkali metal) salt of solid dialkyl succinylsuccinate from an anhydrous supernatant liquid; and (d) neutralizing the di (alkali metal) salt of dialkyl succinylsuccinate to produce the dialkyl succinylsuccinate. The reaction of a dialkyl succinate with a sodium alcoholate to give a di (alkali metal) salt of dialkyl succinylsuccinate according to the present process is described by the following chemical equations: wherein each R is an alkyl group, preferably an alkyl group of 1 to 6 carbon atoms, more preferably an alkyl group of 1 to 3 carbon atoms, and x is a numerical value which is > 0 and < 1. It is preferable that all R groups are equal. The neutralization step is described by the following chemical equation: The process of the invention provides better yields based on the non-recoverable dialkyl succinate, compared to the known processes. For example, the present process generally produces 85 weight percent or more of the dialkylic succinylsuccinate, based on the non-recoverable dialkyl succinate. The non-recoverable dialkyl succinate is the amount charged minus the recoverable amount from all sources. The non-recoverable dialkyl succinate includes the dialkyl succinate which is converted to dialkyl succinylsuccinate, and the dialkyl succinate which can not be counted at the end of the process, which is converted into by-products or lost in the processing of the material. In general, the excess of dialkyl succinate can be recovered from the alcohol distillate of step (b) and the isolation step (c) of the process. The liquid mixtures from these steps can be combined, and the dialkyl succinate and the aliphatic alcohol can be separated to be reused, for example, by fractional distillation. Since there is an excess of the dialkyl succinate, virtually all the alkali metal alcoholate reacts during the course of the reaction. Due to the small amount of byproducts produced, the yields are also at least 85 percent of the theoretical, based on the alkali metal alcoholate. The following is an example of a typical yield calculation when dimethyl succinate (molecular weight = 146) and sodium methylate (molecular weight = 54) are converted to dimethyl succinylsuccinate (molecular weight = 228) in the presence of methanol: by weight of dimethyl succinate (at a purity of 100 percent) loaded = A Parts by weight of sodium methylate (at a purity of 100 percent) loaded = B Parts by weight of succinylsuccinate dimethyl (at a purity of 100 percent) obtained = y Parts by weight of recoverable dimethyl succinate from all sources = z Parts by weight of non-recoverable dimethyl succinate Az Theoretical yield based on sodium methylate = (228x108) x B Theoretical yield based on dimethyl succinate (228x292 ) x (Az) Percentage of succinylsuccinate dimethyl yield = actual yield (y) x 100 theoretical yield The advantages for the environment of the present process are clearly seen by the high yields of the product (dialkynyl succinylsuccinate) and easy recovery of excess dialkyl succinate. Since the anhydrous aliphatic alcohol is generally recovered from the distillate obtained according to step (b) and separation step (c), the anhydrous dialkyl succinate can generally be recovered from steps (b) and (c), and the organic waste material generated by the process of the invention generally consists only of (i) the residue that remains after the dialkyl succinate and any washing solvents are recovered from the isolation step (c), and (ii) a small amount of non-recoverable solvent leaving the neutralization process with the aqueous acid, if the di (alkali metal) salt of dialkyl succinylsuccinate is neutralized as a solvent paste rather than as a dry powder. The dialkyl succinylsuccinates are well known in the art as intermediates for the production of quinacridone pigments. Preferably, the alkyl groups of the dialkyl succinate are two straight or branched alkyl groups, for example, two alkyl groups of 1 to 6 carbon atoms. Preferably, the dialkyl succinate has two alkyl groups of 1 to 3 carbon atoms as the dialkyl substituents. The alkyl groups may be different from one another, but preferably they are the same. More preferably, the dialkyl succinate is dimethyl succinate or diethyl succinate. The dialkyl succinate is combined with an alkali metal alcoholate and an aliphatic alcohol under anhydrous conditions according to the present process. In general, the reaction is best carried out at an elevated temperature, for example, from 60 to 140 ° C, preferably from 90 to 110 ° C. In general, it is convenient to apply a slight vacuum to the system to assist in the removal of the aliphatic alcohol, generated by the reaction, from the reaction mixture. Therefore, a vacuum of 100 to 500 mm Hg can be applied to remove the aliphatic alcohol. Alkali metal alcoholates are known in the art, and are generally prepared by the reaction of an alkali metal with an alcohol. The present process can be carried out using an alkali metal which is added to the dialkyl succinate containing a small amount of aliphatic alcohol under inert anhydrous conditions. The alkali metal alcoholate is preferably formed on site, and reacts with the dialkyl succinate as already described. Since the reaction generates four parts of aliphatic alcohol for each part of the di (alkali metal) salt of formed dialkyl succinylsuccinate, no further addition of aliphatic alcohol is needed when alkali metal is used to generate the alkali metal alcoholate at the site. The generation of the alkali metal alcoholate at the site, therefore, has the advantage of using less aliphatic alcohol. The alkali metal can be added as a solid, preferably added in its molten form. However, alkali metal alcoholates of aliphatic alcohols, for example, are generally preferred. an alkali metal alcoholate of 1 to 6 carbon atoms of alkali metal, or preferably, an alkyl alcoholate of 1 to 3 carbon atoms of alkali metal. Preferably, the alkali metal is sodium or potassium. Preferred alkali metal alcoholates are sodium methylate and sodium ethylate. In general, the alkali metal alcoholates commercially available as a dry powder, or as anhydrous solutions in aliphatic alcohols, are suitable for use in the present process. Any anhydrous aliphatic alcohol is suitable for use in step (a). Preferably, the aliphatic alcohol is an aliphatic alcohol of 1 to 6 carbon atoms. More preferably, the aliphatic alcohol is an aliphatic alcohol of 1 to 3 carbon atoms, such as methanol, ethanol, and 1- or 2-propanol. In general, the commercially available anhydrous aliphatic alcohols are sufficiently anhydrous to be used as the aliphatic alcohol in the present process. Preferably, the alkali metal alcoholate is added to the reaction mixture as an anhydrous solution of 10 to 50 weight percent of the alkali metal alcoholate in the aliphatic alcohol. More preferably, the anhydrous solution is a 25 to 35 weight percent solution of the alkali metal alcoholate in the aliphatic alcohol. Preferably, the anhydrous solution consists only of the alkali metal alcoholate and the aliphatic alcohol.

Suitably 0.1 to 0.5 moles, preferably 0.2 to 0.4 moles, of the alkali metal alcoholate is added to the reaction mixture per mole of liquid dialkyl succinate. It is generally preferred that the alkali metal alcoholate is derived from the same aliphatic alcohol that is used to dissolve it, for example, an anhydrous solution of sodium methylate in methanol or sodium ethylate in ethanol. More preferably, the dialkyl succinate, the alkali metal alcoholate, and the aliphatic alcohol have alkyl groups that are identical. This eliminates the need to separate the alcohols during the recovery processes. For example, a process wherein the dialkyl succinate is dimethyl succinate, the alkali metal alcoholate is sodium methylate, and the aliphatic alcohol is methanol, or the dialkyl succinate is diethyl succinate, the alkali metal alcoholate is sodium ethylate, and the aliphatic alcohol is ethanol. In step (b), the aliphatic alcohol is removed from the reaction mixture by any means known in the art. Preferably, the aliphatic alcohol is removed from the reaction mixture by distillation at atmospheric pressure, or by distillation under reduced pressure, for example, at a reduced pressure of 100 to 500 mm Hg, preferably on the scale of 250 to 500 mm Hg. Step (b) preferably is performed concurrently with step (a). In order to obtain high yields, it is necessary to remove a significant portion of the aliphatic alcohol, which is produced by the reaction and / or is added to the reaction mixture, from the reaction mixture, to allow the temperature to be at a level that promotes reaction. In general, sufficient aliphatic alcohol is removed to maintain the reaction mixture at a temperature greater than about 80 ° C, preferably in the range of 90 to 110 ° C. The removal of the aliphatic alcohol from the reaction mixture initially produces a di (alkali metal) succinylsuccinate dialkyl salt which is a complex formed with dialkyl succinate. The complex is subsequently converted to di (alkali metal) salt of uncomplexed dialkyl succinylsuccinate. In addition to increasing the yield by removing a reaction product, the removal of the aliphatic alcohol serves as an indicator to terminate the reaction because the production of the aliphatic alcohol is stopped when the reaction is finished. Better yields are obtained when the mixture of the precipitated complex of di (alkali metal) salt of dialkyl succinylsuccinate and dialkyl succinate in liquid dialkyl succinate, in the presence of a small amount of the aliphatic alcohol, is maintained at an elevated temperature, preferably at approximately the elevated temperature of step (a), for example, greater than 80 ° C, preferably in the range of 90 to 110 ° C, for a period greater than about 30 minutes, for example, 45 minutes to 2 hours, before converting the di (alkali metal) salt of complexed dialkyl succinylsuccinate, into the di (alkali metal) salt of uncomplexed dialkyl succinylsuccinate. During this period, the aliphatic alcohol is allowed to reflux at atmospheric pressure. At the end of this period, the yield is further improved if the remaining aliphatic alcohol is removed and combined with the other aliphatic alcohol fractions in step (b). If desired, the complex between the di (alkali metal) salt of dialkyl succinylsuccinate and dialkyl succinate is isolated by filtration, and purified by washing with hexane. In general, the complex becomes its constituent parts without being isolated in the reaction mixture. The washed and dried salt complex of di (alkali metal) salt of dialkynyl succinylsuccinate-succinate is characterized by infrared spectroscopy, and is easily distinguished from a physical mixture of di (alkali metal) salt of dialkyl succinylsuccinate and dialkyl succinate . In the case that the alkyl groups are methyl, and the alkali metal is sodium, changes in wavelength are recorded in the region of 1000 to 2000 cm as follows: wavelength complex physical mixture 1742 1740 1654 1646 1520 1518 1434 1440 1386 1386 1326 1322 1244 1252 1182 1196 1162 1164 1074 1078 1004 1002 In general, the di (alkali metal) salt of complexed dialkyl succinylsuccinate is converted to the di (alkali metal) salt of dialkyl succinylsuccinate by the addition of a second anhydrous aliphatic alcohol back to the reaction mixture, but is preferably carried out by transferring the reaction mixture to a second anhydrous aliphatic alcohol with stirring. The second anhydrous aliphatic alcohol may be different from, but preferably is the same as, the aliphatic alcohol of step (a). The amount of the second anhydrous aliphatic alcohol necessary to achieve a good conversion of the complex into its component parts is about 3 to 10 times the weight of the alkali metal alcoholate, preferably 5 to 8 times. The temperature of the reaction mixture before the conversion is generally from about 30 to 120 ° C, but preferably from 90 to 110 ° C. The temperature of the aliphatic alcohol is initially from about 15 to 30 ° C, and is generally from about 30 to 50 ° C after the addition of the reaction mixture. It is convenient to keep the alcoholic paste at a cool temperature (< approximately 30 ° C) before step (c). In general, step (c) is performed by any method employed in the art to separate a solid from an anhydrous liquid. Step (c) is generally carried out by a filtration method, such as press filtration, roller, or sheet filter, or by a centrifugal method. Since the reaction mixture is preferably combined with a second anhydrous aliphatic alcohol in step (b) to convert the complex to the di (alkali metal) salt of dialkyl succinylsuccinate, the supernatant from step (c) is generally a anhydrous mixture of the dialkyl succinate and an aliphatic alcohol. Step (c) preferably includes several washing steps, wherein the di (alkali metal) salt of solid dialkylisuccinyl succinylsuccinate is washed with an anhydrous solvent to remove excess dialkyl succinate and solvent soluble by-products. Preferably, the anhydrous solvent used for washing does not react with, or dissolve, appreciable amounts of the salt. In general, the commercially available anhydrous solvents are sufficiently anhydrous to be used as the anhydrous wash solvent in the present process. More preferably, the anhydrous solvent is easily separated from the dialkyl succinate which is washed out of the solid salt, for example, by distillation, at atmospheric or reduced pressure. Suitable solvents include anhydrous lower aliphatic alcohols, ketones, ethers, and hydrocarbon solvents, or aromatic ethers or hydrocarbons or mixtures of these solvents. In particular, the anhydrous solvent is an aliphatic alcohol of 1 to 6 anhydrous carbon atoms. Preferably, the aliphatic alcohol is an aliphatic alcohol of 1 to 3 carbon atoms, such as methanol, etapol, and 1- or 2-propanol. More preferably, the anhydrous solvent is an aliphatic alcohol of 1 to 3 carbon atoms which is identical to the aliphatic alcohol used in step (a) and the second anhydrous aliphatic alcohol used for the conversion in step (b). According to step (d), the di (alkali metal) salt of dialkyl succinylsuccinate is neutralized to produce the succinylsuccipate dialkyl, which can be isolated or used as a reagent for the production of quinacridones without isolation. In general, the di (alkali metal) salt of dialkyl succinylsuccinate is neutralized simply by mixing it with an acid, preferably an aqueous mineral acid, for example, hydrochloric acid, sulfuric acid, phosphoric acid, or carbonic acid, or an aqueous organic acid , such as formic acid or acetic acid. Preferably, aqueous sulfuric acid is used. Preferably, the aqueous mineral acid is a solution of 10 to 20 weight percent of a mineral acid in water, for example, a 15 weight percent solution of sulfuric acid in water. An amount of acid which converts all the di (alkali metal) salt of dialkyl succinylsuccinate to dialkynyl succinylsuccinate is generally selected., and which ends with a pH of the aqueous mother liquor in the scale from 1 to 7, preferably from 3 to 6. The di (alkali metal) salt of washed dialkyl succinylsuccinate is neutralized in step (d) as a dry powder (obtained, for example, by drying with heated nitrogen), as a wet solid directly from the isolation device, or as a slurry which can be pumped by reconstituting the di (alkali metal) salt of dialkyl succinylsuccinate with fresh anhydrous solvent . If the dialkylic succinylsuccinate is isolated, it is generally isolated by the methods described above to separate a solid from a liquid. The residual water-soluble salts from the neutralization process, and the water-soluble organic residues on the dialkyl succinylsuccinate, are removed by an appropriate washing, generally with water, which can be softened, deionized, or artificially distilled. The dialkyl succinylsuccinate can be dried (for example, in a vacuum paddle dryer), or it can be used in the following steps as a wet solid or as a pumpable slurry. From the above discussion, it is clear that the preferred embodiments of the present process include additional process steps. For example, a preferred embodiment includes the following steps: (a) producing a di (alkali metal) salt of dialkyl succinylsuccinate by reaction of a mixture consisting essentially of an alkali metal alcoholate, an aliphatic alcohol, and an excess of a dialkyl succinate at elevated temperature under anhydrous conditions; (b) removing a substantial portion of the aliphatic alcohol from the reaction mixture, subsequent to, or concurrent with, step (a); (bl) maintaining the reaction mixture resulting from step (b) at an elevated temperature, such as the reflux temperature, for a period greater than 30 minutes; (b2) optionally remove the remaining aliphatic alcohol; (b3) combining the reaction mixture with a second aliphatic alcohol to produce the di (alkaline metal) salt of uncomplexed dialkyl succinylsuccinate in an anhydrous supernatant liquid; (c) separating the di (alkali metal) salt of dialkyl succinylsuccinate from the reaction mixture; (d) neutralizing the di (alkali metal) salt of dialkyl succinylsuccinate to produce a dialkyl succinylsuccinate; and (di) optionally, recovering the dialkyl succinate and / or the aliphatic alcohol of steps (b) and (c) to be reused. In general, steps (b), (bl), (b2), and (b3) are performed in sequence. In a preferred embodiment of the present process, step (a) is carried out by adding an anhydrous solution of the alkali metal alcoholate in the aliphatic alcohol, to the liquid dialkyl succipate. In general, 0.1 to 0.5 moles, preferably 0.2 to 0.4 moles, of the alkali metal alcoholate per mole of liquid dialkyl succinate are added. Normally, the anhydrous solution is added to the liquid dialkyl succinate for a prolonged period of time, for example, for about 30 minutes to about 4 hours, for example, at a rate of 0.01 to 0.1 parts by weight of the alkali metal alcoholate by hour per part of the dialkyl succinate. As the ahydrous solution is added to the liquid dialkyl succinate, the alcohol is removed by distillation, for example, under reduced pressure. Accordingly, the present process encompasses a process wherein the alcohol is removed from the reaction mixture by distillation under reduced pressure concurrently with the addition of the anhydrous solution to the dialkyl succinate. The preferences discussed above also apply to the preferred mode. For example, it is preferable that the dialkyl succinate, the alkali metal alcoholate, and the aliphatic alcohols have alkyl groups that are identical, for example, that the dialkyl succinate is dimethyl succinate, that the alkali metal alcoholate is sodium methylate, and that the aliphatic alcohols are methanol, or that the dialkyl succinate is diethyl succinate, the alkali metal alcoholate is sodium ethylate, and the aliphatic alcohol is ethanol. It is also preferable that the alkali metal alcoholate is added as a solution of 10 to 50 weight percent of an alkali metal alcoholate in the alcohol. In addition, as described above, it is preferable to maintain the di (alkali metal) salt complex of solid dialkyl succinylsuccinate and dialkyl succinate in liquid dialkyl succinate at an elevated temperature over a period of 45 minutes at? hours before step (c), that the anhydrous solvent used in the washings is an aliphatic alcohol of 1 to 3 carbon atoms, more preferably identical to the aliphatic alcohol of step (a), and that the di (alkali metal) salt of dialkylic succinylsuccinate is neutralized with aqueous sulfuric acid. A further objective of the present invention is a novel complex of the formula: wherein M is an alkali metal, each R is independently alkyl of 1 to 6 carbon atoms, and x is a numerical value which is > 0 and < _1, preferably wherein M is sodium or potassium, and each R is independently alkyl of 1 to 3 carbon atoms. The complex is an intermediate in the present process that can be isolated and purified, for example, by filtration and washing with an inert solvent, before further processing, or separated into its constituent parts without isolation. The dialkyl succinylsuccinate products of the present process are useful intermediates in the preparation of quinacridone pigments. Therefore. The present invention also relates to a process for the preparation of a quinacridone compound of the formula: wherein each R is independently hydrogen, alkyl of 1 to 6 carbon atoms unsubstituted or substituted, preferably methyl, ethyl, or trifluoromethyl, halogen, preferably chlorine or fluorine, alkoxy of 1 to 6 carbon atoms unsubstituted or substituted, preferably methoxy or ethoxy, -COOR wherein R 1 is hydrogen or alkyl of 1 to 6 carbon atoms; alkyl groups of 1 to 6 carbon atoms or alkoxy of 1 to 6 carbon atoms substituted, which are substituted by one or more customary substituents, such as halogen, nitro, -OH, or -COORj; said process comprises: (a) preparing a di (alkali metal) salt of dialkyl succinylsuccinate by reaction of a mixture consisting essentially of an alkali metal alcoholate, an aliphatic alcohol, and an excess of a liquid dialkyl succinate under anhydrous conditions at an elevated temperature; (b) removing the aliphatic alcohol from the reaction mixture; (c) separating the di (alkali metal) salt of solid dialkyl succinylsuccinate from an anhydrous supernatant liquid; (d) neutralizing the di (alkali metal) salt of dialkyl succinylsuccinate to produce the dialkyl succinylsuccinate, and (e) converting the dialkyl succinylsuccinate to the quinacridone. Preferably, the quinacridone is selected from the group consisting of quinacridone, 2,9-dichloroquinacridone, 2,9-dimethylquinacridone, and 4,11-dichloroquinacridone. Steps (a) - (d) were described above. Step (e) is performed by processes that are well known in the art. For example, the dialkyl succipylsuccinate is converted to a quinacridone by (aa) condensation with an aniline in the presence of an acid catalyst in a solvent to give a dialkyl 2,5-dianilino-3,6-dihydroterephthalate, which can be isolated or it can be reacted directly; (bb) add the product of (aa) to a high-boiling liquid (boiling point of at least 250 ° C) at its boiling point with alcohol removal, to produce a dihydroquinacridone; and (ce) oxidizing the dihydroquinacridone product of step (bb) with a suitable oxidant in an alkaline medium to produce the quinacridone. The substitution of the aniline used in step (aa) controls the substitution of the quinacridone end product, for example, para-chloroaniline produces 2,9-dichloroquinacridone, and para-toluidine produces 2,9-dimethylquinacridone. The following examples describe the embodiments of the invention, but do not limit the invention. All parts are parts by weight unless otherwise specified.Example 1: A 30 percent solution of sodium methylate (55.0 grams, 1.02 moles) in dry methanol (126.5 grams, 3.95 moles) at 30 ° C under nitrogen, is added for 2 hours by means of a peristaltic pump to succinate agitated dimethyl (493.9 grams, 3.38 moles) at 105 ° C (± 5 ° C) at a pressure of 350 to 400 mm Hg. The methanol is distilled through a short column to a graduated receiver. Upon completion of the addition, the vacuum is replaced by nitrogen at atmospheric pressure, the condenser is switched to reflux, and the elevated temperature is maintained for 1 hour. The residual methanol is subsequently distilled for an extra period of 1 hour to remove the last traces of methanol. The resulting slurry is cooled to less than 50 ° C, then pumped to dry stirred methanol (320 grams, 10.0 moles), and maintained at less than 30 ° C. After verifying under the microscope that the complex has been converted To the crystalline form of the disodium salt of succinylsuccinate dimethyl, the mixture is filtered using an inert Buchner funnel. The filter cake is washed with anhydrous methanol, if necessary by re-forming the slurry in anhydrous methanol, followed by filtration. This washing step is repeated until the methanol washes contain less than 0.3 percent dimethylsuccinate by gas chromatography. The combined filtrates are collected for fractionation in order to recover methanol and dimethyl succinate. The filter cake wet with methanol is transferred, with stirring, to a neutralization vessel containing 15 percent aqueous sulfuric acid (332.7 grams, 0.51 moles) at room temperature under nitrogen. After 1 hour at 30-35 ° C, the product of dimethylsuccinylsuccinate is filtered. The press cake is subsequently washed with water at 30-35 ° C, if necessary re-forming the slurry in water, followed by filtration. This washing process is repeated until the filtrates show less than 0.5 percent methanol by gas chromatography, the pH is greater than 6.0, and the conductivity is within 5 percent of the inlet wash water. The cake of the press wet with water is weighed, and a sample is taken to see the solids content and for the analysis. The yield of 100 percent pure dimethyl succinylsuccinate based on sodium methylate is 86 percent.

Example 2: Example 1 is repeated, except that the dimethyl succinate is formed from dimethyl succinate recovered from the distillation of the combined filtrates of various embodiments of Example 1. The yield of succinylsuccinate dimethyl, based on sodium methylate, is 87.5 percent of the theoretical.

Example 3: A 30 percent solution of sodium methylate (55.5 grams, 98.6 percent purity, 1.01 moles) in dry methanol (126.5 grams, 3.95 moles) at 30 ° C under nitrogen, is added for 1 hour per medium from a peristaltic pump to the stirred dimethyl succinate (385.1 grams, purity 98.7 percent, 2.60 moles) at 105 ° C, at a pressure of 400 mm Hg. The methanol is distilled through a short column to a cooled graduated receiver. At the end of the addition, the vacuum is replaced by nitrogen at atmospheric pressure, the condenser is switched to reflux, and the elevated temperature is maintained for 1 hour. The residual methanol is then distilled to give 196 grams of the distillate (it contains 3.8 percent dimethyl succinate by gas chromatography analysis). The resulting slurry is cooled to 50 ° C, then pumped to dry stirred methanol (444 grams, 13.9 moles), and maintained at 25-30 ° C. After checking under the microscope that the entire complex has been converted to the crystalline form of the disodium salt of succinylsuccinate dimethyl, the mixture is filtered using an inert Buchner funnel. The filter cake is washed with anhydrous methanol (475 grams, 14.8 moles) until the methanol washings contain less than 0.3 percent dimethyl succipate by gas chromatography. The filter cake wet with methanol is re-formed into a slurry in dry methanol (237 grams, 7.4 moles), and transferred to stirred 15 percent aqueous sulfuric acid (328 grams, 0.50 moles) at room temperature under nitrogen. After 1 hour at 30-35 ° C, the dimethyl succipylsuccinate is filtered. The press cake is washed with water at 30-35 ° C until the filtrate shows less than 0.5 percent methanol by gas chromatography. the pH is greater than 6.0, and the conductivity is within 5 percent of the inlet wash water. The press cake wet with water is dried in a vacuum oven at 50 ° C to give 99.3 grams of dimethyl succinylsuccinate of a purity of 99.5 percent for an 86 percent yield of the theoretical, based on sodium methylate.

Example 4: To a stirred solution of dimethyl succinate (400.1 grams, purity of 98.7 percent, 2.7 moles) and dry methanol (13 grams, 0.4 moles) at 30 ° C under nitrogen, a stirred slurry is added for 1.5 hours. finely divided sodium (22.1 grams, 0.96 moles) in dimethyl succinate (83.4 grams, 0.57 moles). The temperature rises to 45 ° C maximum. The mixture is heated to 76 ° C and the methanol is separated for 2 hours. Additional dimethyl succinate (200 grams, 1.38 moles) is added to maintain the flowability of the reaction. At the end of the methanol distillation, methanol (400 grams, 12.5 moles) is added, and the mixture is cooled to 30 ° C, filtered, and the excess of dimethyl succinate is washed with dry methanol. The resulting filter cake is re-formed into a paste in methanol, and added to 15 percent aqueous sulfuric acid (330 grams), cooled to 24 ° C, then filtered, washed with water to remove the sulfate. of sodium, and it dries. A yield of 81 percent of the dimethylsuccinylsuccinate of theory is obtained.

Example 5: Dimethyl succinate (165,564 kg, 1134 kg mol) is charged in a 378.54 liter stainless steel reactor, and the vessel is made inert with nitrogen, then heated to 100-105 ° C. A vacuum of 355.6 is applied. mm Hg with a nitrogen purge, and the dimethyl succinate is separated from any residual moisture. A solution of 30 percent sodium methylate in methanol (81,648 kg, 0.4536 kg mol) is added by means of a peristaltic pump at a rate of approximately 0.3402 kg / minute. The methanol (with any dimethyl succinate fed) is distilled and collected in a cooled receiver. The addition rate is adjusted to maintain the container temperature at 105 ° C. Upon completion of the addition, the mixture is allowed to reflux at atmospheric pressure under nitrogen for 1 hour. Vacuum is reapplied, and the residual methanol is separated and added to the receiver. The reaction slurry is cooled to 90 ° C and transferred to a second vessel containing stirred dry methanol (181.44 kg) at 25 ° C. At the end of the transfer, the residual slurry is rinsed with dry methanol (22.68 kg), and the methanolic slurry is stirred for 1 hour. The disodium succinylsuccinate dimethyl salt paste is fed to a centrifuge, and the mother liquors are removed. The cake is washed with dry methanol until the washes contain less than 0.3 percent dimethyl succinate. Nitrogen is heated and used to dry the cake on the centrifuge before transferring the dry powder to a collection bag. The disodium salt of dry dimethyl succinylsuccinate is then added to a stirred solution of 15 percent aqueous sulfuric acid (251.7437 kg) at 25 ° C. The product is filtered by centrifugation and washed with water until the filtrates show a pH > 6.0 and the conductivity is within 5 percent of the incoming water. It is convenient to use deionized water in the final stages. The product is dried in a vacuum paddle dryer. The yield is 85 percent of the theory. The excess of dimethyl succinate and dry methanol is recovered from the combined upper portions and the filtrates by fractional distillation through a packed column. Both are suitable to be reused in the reaction without further purification. Distillation residues dissolve in water and are sent to waste neutralization.

Example 6: The dimethyl succinylsuccinate of Example 5 (22.8 grams, 0.1 mole) is dissolved in THERMINOL VP-1 (a mixture of diphenyl ether and biphenyl of Monsanto, 129.2 grams) at 90 ° C under nitrogen, and added for 1 hour to a stirred mixture of aniline (23.25 grams, 0.25 moles), THERMINOL VP-1 (85 grams), and trifluoroacetic acid (0.5 grams) at 90 ° C and 100 mm Hg pressure. The water is removed from the condensation, and at the end of the condensation, the pressure is lowered to 15 mm Hg, and excess aniline, trifluoroacetic acid, and a part of THERMINOL VP-1 are distilled, replacing the distillate volume with an equal volume of fresh THERMINOL P-1, until the distillate shows less than 0.1 percent aniline . The product, 2,5-dianilino-3,6-dihydroterephthalate dimethyl, is diluted to a 10 percent paste with THERMINOL P-1, and heated to a solution at 160-170 ° C. This solution is added during 3 hours at THERMINOL YP-1 in rapid stirring and vigorous boiling under nitrogen. The methanol, with the THERMINOL VP-1 fed, is collected by distillation. At the end of the addition, the boiling is continued for 1 hour, the slurry is cooled to 180 ° C, and filtered. The dihydroquinacridopa is collected by filtration and washed to liberate THERMINOL vP-1 with methanol. The yield is approximately 30 grams after drying. The dihydroquinacridone is formed in a slurry in methanol (120 grams), and 50 percent sodium hydroxide (18 grams) is added with stirring, keeping the temperature below 45 ° C. After stirring for 1 hour at 45- 55 ° C, 96 percent sulfuric acid (3 grams) is added, followed by water (33 grams), and the mixture is heated to reflux. After refluxing for 1 hour, sodium m-nitrobenzenesulfonate (17.25 grams) is added, followed by water (19.5 grams) and refluxing is continued for 3 hours. Sufficient water is added to obtain a temperature of 60 ° C, and the mixture is filtered and washed with hot water until the pH of the filtrate is less than 8.5 and the conductivity of the filtrate is within 10 percent of that of the water. entry. Then the t-quinacridone, an opaque, bright red pigment, is dried and ground. The yield from dimethyl succinylsuccinate is 93 percent of theory.

Example 7: In a manner similar to Example 6, with the substitution with an equi-olar proportion of p-chloroaniline by the aniline, 2,9-dichlorodihydroquinacridone is obtained. The oxidation of 2,9-dichlorodihydroquinacridone (40 grams) is carried out by the addition of methanol (160 grams), 45 percent potassium hydroxide (160 grams), and stirring for 15 minutes at 50-60 ° C. sodium m-nitrobenzenesulfonate (23 grams) is added, followed by water (26 grams), and the mixture is heated to reflux and refluxed for 3 hours. Water is added to the mixture to obtain a temperature of 60 ° C, and the paste is filtered and washed with hot water until the filtrate shows a pH lower than 8.5 and the conductivity of the filtrate is within 10 percent of that of the water input. The product, 2,9-dichloroquinacridone, a magenta pigment, is dried and pulverized. The yield from dimethyl succinylsuccinate is approximately 92 percent of theory.

Claims (20)

1. A process for the preparation of a dialkyl succinylsuccinate, which comprises: (a) preparing a di (alkali metal) salt of dialkyl succinylsuccinate by reaction of a mixture consisting essentially of an alkali metal alcoholate, an aliphatic alcohol, and an excess of a liquid dialkyl succinate under anhydrous conditions at an elevated temperature; (b) removing the aliphatic alcohol from the reaction mixture; (c) separating the di (alkali metal) salt of solid dialkyl succinylsuccinate from an anhydrous supernatant liquid; and (d) neutralizing the di (alkali metal) salt of dialkyl succinylsuccinate to produce the dialkylic succinylsuccinate.

2. A process of claim 1, wherein the percent yield, based on the reacted dialkyl succinate, is at least 85 percent by weight.

3. A process of claim 1, wherein liquid dialkyl succinate is recovered from step (c), and recycled after purification, to a subsequent step (a).

4. A process of claim 1, wherein the dialkyl succinate has two alkyl groups of 1 to 3 carbon atoms as the dialkyl substituents, and is preferably dimethyl succinate or diethyl succinate.

5. A process of claim 1, wherein the alkali metal alcoholate is an alkali metal alcoholate of 1 to 3 carbon atoms, preferably a sodium or potassium alkoxide, more preferably sodium methylate or sodium ethylate.

6. A process of claim 1, wherein the aliphatic alcohol of step (a) is an aliphatic alcohol of 1 to 3 carbon atoms.

7. A process of claim 1, wherein the alkali metal alcoholate is prepared on site.

8. A process of claim 1, wherein the alkyl groups of the dialkyl succinate, the alkali metal alcoholate, and the aliphatic alcohol are identical.

9. A process of claim 8, wherein the dialkyl succinate is dimethyl succinate, the alkali metal alcoholate is sodium methylate, and the aliphatic alcohol is methanol. A process of claim 1, wherein the alkali metal alcoholate and the aliphatic alcohol are combined with the dialkyl succinate as a solution of 10 to 50 weight percent, preferably 25 to 35 weight percent of the alcoholate of alkali metal in the aliphatic alcohol. 11. A process of claim 1, wherein 0.1 to 0.5 moles, preferably 0.2 to 0.4 moles, of alkali metal alcoholate is added to the reaction mixture per mole of dialkyl succinate. 12. A process of claim 1, wherein the aliphatic alcohol is removed according to step (b) by distillation under reduced pressure, preferably wherein the aliphatic alcohol is removed concurrently with the addition of a 25 to 35 solution. percent by weight of the alkali metal alcoholate in the aliphatic alcohol, to the dialkyl succinate. 13. A process of claim 12, wherein a suspension formed in accordance with step (b) is maintained at the elevated temperature, for a period of 45 minutes to 2 hours before step (c). 14. A process of claim 13, wherein the di (alkali metal) salt of dialkyl succinylsuccinate is neutralized with aqueous sulfuric acid. 15. A process of claim 1, wherein the di (alkali metal) salt of dialkyl succinylsuccinate is in the form of a complex with the dialkyl succinate after step (b), and the complex is converted to the di ( alkali metal) of uncomplexed dialkyl succinylsuccinate before passage (c), by combining the reaction mixture with a second anhydrous aliphatic alcohol, which is the same as or different from the aliphatic alcohol used according to step (a). 16. A process of claim 15, wherein the second anhydrous aliphatic alcohol is an aliphatic alcohol of 1 to 3 carbon atoms, preferably wherein the aliphatic alcohol of 1 to 3 carbon atoms is identical to the aliphatic alcohol of the step ( to) . 17. A process of claim 1, wherein step (c) includes one or more wash steps, wherein the di (alkali metal) salt of dialkyl succinylsuccinate is washed with an anhydrous organic solvent, preferably wherein the Anhydrous organic solvent is an aliphatic alcohol of 1 to 3 carbon atoms. 18. A complex of the formula: wherein M is an alkali metal, each R is independently alkyl of 1 to 6 carbon atoms, and x is a numerical value which is > 0 and < _1, preferably wherein M is sodium or potassium, and each R is independently alkyl of 1 to 3 carbon atoms. 19. A process for the preparation of a quinacridone compound of the formula: wherein each R is independently hydrogen, alkyl of 1 to 6 carbon atoms unsubstituted or substituted, halogen, alkoxy of 1 to 6 carbon atoms, unsubstituted or substituted, or -COORj, wherein Rj is hydrogen or alkyl of 1 to 6 carbon atoms; said process comprises: (a) preparing a di (alkali metal) salt of dialkyl succinylsuccinate by reaction of a mixture consisting essentially of an alkali metal alcoholate, an aliphatic alcohol. and an excess of a liquid dialkyl succinate under anhydrous conditions at an elevated temperature; (b) removing the aliphatic alcohol from the reaction mixture; (c) separating the di (alkali metal) salt of solid dialkyl succinylsuccinate from an anhydrous supernatant liquid; and (d) neutralizing the di (alkali metal) salt of dialkyl succinylsuccinate to produce the dialkylic succinylsuccinate, and (e) converting the dialkyl succinylsuccinate in quinacridone. 20. A process of claim 19, wherein the quinacridone is selected from the group consisting of quinacridone, 2,9-dichloroquinacridone, 2,9-dimethylquinacridone, and 4,11-dichloroquinacridone.