DE3031325A1 - Tetra:alkyl ethane-1,1,2,2-tetra:carboxylic acid ester prepn. - by di:alkyl malonate condensate with halogenating agent in presence of alkali hydroxide soln. - Google Patents

Abstract

Tetra-alkyl ethane-1,1,2,2-tetracarboxylic acid esters, (I) are prepd. by condensing dialkyl malonates, (II), with the required halogenating agent quantity to form 1 mol. (I) out of 2 mol (II) in the presence of bases. Novelty consists in usinq, as base, aq. lyes, esp. alkali hydroxide-, partic. aq. NaOH solns., under the formation of a 2-phase system. (II) are esp. the 1-6C alkyl esters, esp. the Me- or Et esters. The halogenating agents can be Br2 (prefd.), alkali hypobromite, CBrCl3 and/or N-bromo-succinimide. Molar ratio halogenating agent: (II) is 1:2. The reaction mixt. is pref. diluted with an aq. base-immiscible organic solvent, esp. CH2Cl2 or carbon tetra-chloride, which dissolve (I) and allow the easy separation of (I). (I) are intermediates for the prepn. ef the free ethane- 1,1,2,2-tetracarboxylic acids and their salts, used esp. as builders in deteroent compsns. the H2O2 adducts of the alkali- and ammonium salts can also be used as deterqent builders and also as complexing agents and H2O2-sources. (I) are obtd. in high yields by a simple, cheap process.

Description

Process for the production of ethane-1,1,2,2-tetracarboxylic acid

tetraalkyl esters Ethane-1,1,2,2-tetracarboxylic acid tetraalkyl esters are compounds of the formula I below (R = alkyl radicals) They are mainly intermediate products for the preparation of the free ethane-1,1,2,2-tetracarboxylic acid and its salts, which in turn are used in particular as images in detergent formulations (see, for example, RS-PS 3 829 384). The H 2 O 2 adducts of the alkali and ammonium salts also serve as detergent builders and also as complexing agents and H 2 O 2 sources (cf. US Pat. No. 3,929,875).

For the preparation of ethane-1,1,2,2-tetracarboxylic acid tetraalkyl esters a large number of processes are known An overview of the most common processes gives e.g. Beilstein E II2 p. 857 (system no. 189). Most of the procedures pass in a condensation of the corresponding Malonsäuredialklester in Geqenwa rt one Halogenating agent (especially bromine) and a base.

The base is generally sodium or metallic to sodium alcoholate. In the case of such, starting from diethyl malonate The process is carried out with bromine as the alogenating agent and sodium in absolute ethanol as base medium 80% of theory of ethane-1,1,2,2-tetacarboxylic acid-tet-thviester obtained [J.Amer.Soc. 78, 28O8 / 9 (1 956) 2. With this as well as with practically all known ones similar The process must be carried out in a completely or largely water-free medium. In addition, the bases used are not always easy to handle (well!) and therefore often require special safety precautions.

The task was therefore to find a simpler and more economical one Process for the preparation of ethane-1,1,2,2-tetracarboxylic acid tetraalkyl esters too Find.

This task could be achieved in the condensation of dialkyl malonates be solved according to the invention by the use of aqueous alkalis.

The subject of the invention is therefore a process for the preparation of ethane-1,1,2,2-tetracarboxylic acid tetraalkyl esters from malonic acid dialkyl esters and a halogenating agent in the form of 1 mol of ethane-1,1'2,2-tetracarboxylic acid tetraalkyl ester from 2 mol of malonic acid dialkyl ester required amount in the presence of bases; the procedure is characterized by that the bases used are aqueous alkalis with the formation of a 2-phase system.

int with regard to the single state of the art, according to which at Such condensations have always been worked in anhydrous solutions (or had to be), it was extremely surprising that the condensation now also with aqueous alkalis smoothly and with high yields of the desired end product is feasible.

As a malonic acid dialkyl ester can practically all in the process possible alkyl esters of malonic acid are used; however, that is preferred Use of the (C1-C6) -alkyl esters, in particular the methyl and ethyl esters.

As the halogenating agent, a variety of can be used for such purposes known halogen-containing substances, such as e.g.

elemental chlorine, bromine and iodine, alkali hypobromite, alkali hypochlorite, Bromotrichloromethane, N-bromosuccinimide, N-chlorosuccinimide, etc. Elemental are preferred Bromine, alkali hypobromite, bromotrichloromethane and N-bromosuccinimide, especially elemental Bromine.

If elemental bromine is used, about 1/2 mole of bromine is required per mole of malonic ester, as can be seen from the following reaction equation on which the process is based: Corresponding amounts of the other possible halogenating agents should be used. In the case of the preferred halogenating agents, this is also about 1/2 mole per mole of starting malonic ester. An excess of halogenating agent easily leads to a further reaction (# ethene-tetracarboxylic acid tetraalkyl ester) and should therefore be avoided as far as possible.

Preferred aqueous alkalis are aqueous alkali hydroxides, in particular aqueous sodium hydroxide solution. The concentration of the lye should be used to reduce the Saponification of the carboxyalkyl groups should not be too low. The lye can easily used in excess; an excess of at least about 10% over the stoichiometric Amount in addition is even preferred.

Since the malonic acid dialkyl ester as well as the ethane-1,1,2,2-tetracarboxylic acid tetraalkyl ester are not mixed with aqueous lukewarm, the reaction takes place in the 2-phase system instead of.

However, it is generally advantageous to use the reaction mixture with eir.e organic solvent, which with Water under the Reaction conditions is not very miscible, to be diluted.

For this purpose, dichloromethane or carbon tetrachloride come in Question. These solvents are advantageous in that the reaction products are soluble in them and thus isolation can be easily achieved.

The implementation can be both in the presence and in the absence of a Phase transfer catalyst can be carried out, with the presence of such Catalyst is preferred. Such a catalyst increases the rate of the reaction and thus reduces the reaction time and also the saponification of the ester groups. The main phase transfer catalysts used are quaternary ammonium and phosphonium salts (especially the halides) in question.

Their amount is advantageously in the range from about 0.05 to 10 percent by weight , preferably from about 0.3 to 3 percent by weight, based on the starting material.

The reaction temperature is generally between about -200C and about + 1000C, but preferably between about -5 and about + 200C.

The reaction can be either batchwise or continuously be performed.

The dialkyl malonate can be initially charged, then the lye can are added dropwise and finally the alcoholic agent; or the lye can The malonic acid ester and then the halogenating agent are then presented.

But also a presentation of the halogenating agent or another Form of addition is possible.

Preference is given to initially taking the lye with the organic solvent and, if necessary, the phase transfer Catalyst. To be the dialkyl malonate and the halogenating agent are added at the same time, a slight excess of dialkyl malonate being present at the beginning of the reaction should be.

After the reactants have been added, stirring is continued for a short time.

If the reaction is carried out continuously, it should preferably all in one second reaction vessel.

After the reaction has ended, the reaction mixture can be acidified and washed or processed directly.

To isolate the product, the organic of separated the aqueous phase, washed this with the organic solvent, the combined organic phase is also dried over sodium sulfate or the solvent is distilled off directly from this. The raw product has at appropriated The reaction is sometimes carried out with a purity of> 90% and can possibly be carried out directly continue to be used. Becomes a purer ethane-1,1,2,2-tetracarboxylic acid tetraalkyl ester if desired, the crude product can be further processed by distillation or crystallization be united.

The aqueous phase can be used to regenerate the halogenating agent be worked up.

Because of the simple and cheap feasibility of the procedure as well the good to very good yields of ethane-1,1,2,2-tetracarboxylic acid tetraalkyl esters the invention represents a not inconsiderable advance.

The invention will now be explained in more detail by the following examples.

The implementation of the earth. in glass barrel, the m3 4 two Add dropping funnels, reflux condenser, internal thermometer, stirrer and external cooling are.

Example 1 To an emulsion of 100 ml of 25% sodium hydroxide solution ad 400 ml of methylene chloride in which 200 mg of tetraburtylammonium bromide are dissolved while stirring at 2 ° -40 ° C. within 35 minutes, 4.60 g (28.7 mmol) of diethyl malonate were obtained and then 41.44 g (258.7 mmol) and 30.0 g (151.3 mmol) of bromotrichloromethane in 25 ml Methylene chloride was added dropwise. It is left for 30 minutes at constant temperature and then stir for 90 minutes without cooling. The phases are separated, the aqueous phase is extracted with methylene chloride, the combined methylene chloride phase is with Hydrochloric acid acidified, the aqueous phase separated, the organic phase over atrium sulfate dried and the solvent removed. The crude product obtained is 45.5 g, which is recrystallized with ethanol, 37.7 g (82.4% of theory).

M.p. 72-730C.

Example 2 Reaction as in Example 1. The brominating agent is -Li-Bropt-succinimide used in methylene chloride. Yield 63%.

Schm. 67-730C.

Example 3 Reaction as in Example 1. The brominating agent is a stoichiometric amount of bromine is used with respect to the malonic acid diethyl ester. No phase transfer catalyst is added. In contrast to the reaction with Catalyst becomes a clear dependence of the bromine discoloration on the stirring speed established. Crude product 91%.

After crystallization 62% with m.p. 73-740C and off the Mother liquor 17% with m.p. 62-660C.

1 H NMR (CDCl3): 1.26 ppm (T, 12 H); 4.10 ppm (S, 2 H); 4.20 ppm (Quartet, 8 H).

Example 4 Reaction analogous to Example 3. Addition of 200 mg of tetrabuty3-ammonium bromide. Reaction temperature -200C. After the addition has ended, stir for 100 minutes without cooling. Crude product 93%.

After crystallization 65 gO with melting point 72-74.5 ° C.

Example 5 Reaction as in Example 4. Addition temperature of the brominating agent + 200C. Crude product 86%. After recrystallization 49% with m.p. 70-740C.

Example 6 Reaction analogous to Example 4. Reaction temperature fdOoc (Reflux of CH2Cl2), reaction time 30 minutes. Poh product 90%. After recrystallization 46% with m.p.

70-720C.

Example 7 Reaction analogous to Example 4. Tetrachloromethane solvent. Reaction temperature + 77 ° C. Crude product 33 t. After crystallization 16% with m.p. 67-700C.

Example 8 As in Example 3, dimethyl malonate is obtained with 50% strength Soda water and a stoichiometric amount of bromine in the presence of 0.3% tetrabutylammonium bromide implemented at -10 to + 20C and acidify o @ e, worked up. Raw product 80 t. After crystallization from methanol, 53% yield with melting point 134-1370C.

1 H NMR (CDCl3) 3: 3.77 ppm (S, 12 H); 4.17 ppm (S, 2 H).

Claims (8)

Patent claims: Process for the preparation of ethane-1,1,2,2-tetracarboxylic acid tetraalkyl esters from malonic acid dialkyl esters and a Halogenierungsm.i ttel in the for formation of 1 mole of ethane-1,1,2,2-tetracarboxylic acid tetraalkyl ester from 2 moles of dialkyl malonate required amount in the presence of bases, characterized in that as Bases, aqueous alkalis are used to form a 2-phase system. 2. The method according to claim 1, characterized in that as Dialkyl malonate, the (C1-C6) -alkyl esters, in particular the methyl or ethyl esters used. 3. The method according to claims 1 to 2, characterized in that that the halogenating agent used is elemental bromine, alkali hypobromite, bromotrichloromethane and / or N-bromosuccinimide, especially elemental bromine, is used. 4. The method according to claim 3, characterized in that the Halogenating agent in an amount of about 1 mole / 2 moles dialkyl malonate begins. 5. Process according to claims 1 to 4, characterized in that that the aqueous alkaline solutions are aqueous alkali metal hydroxides, in particular aqueous sodium hydroxide solution, used. 6. The method according to claims 1 to 5, characterized in, that the reaction mixture is a little miscible with the aqueous base organic Solvent, preferably dichloromethane or tetrachloromethane added. 7. Expires according to claims 1 to 6, dadijrch ckenii- draws, that the reaction mixture is a phase transfer catalyst, preferably a quaternary ammonium or phosphonium salt added. 8. Process according to claims 1-7, characterized in that one the reaction at temperatures between about -20 and + 100 ° C, preferably between about -5 and about + 200C.