WO2007074063A1

WO2007074063A1 - Method for the production of 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine

Info

Publication number: WO2007074063A1
Application number: PCT/EP2006/069637
Authority: WO
Inventors: Oliver Stratmann
Original assignee: Wacker Chemie Ag
Priority date: 2005-12-22
Filing date: 2006-12-13
Publication date: 2007-07-05
Also published as: DE102005061577B3

Abstract

The invention relates to a method for recovering 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine. Said method comprises the following steps: a) the optionally insoluble fractions are eliminated from a solution containing 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine in a polar aprotic solvent; b) the obtained solution is concentrated, and the precipitate formed during said process is eliminated; and c) the precipitate is optionally recrystallized from a polar aprotic solvent. Also disclosed is a method for producing 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine from 2,4-dioxohexahydro-1,3,5-triazine, 1-acetyl-2,4-dioxohexahydro-1,3,5-triazine, or 1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine by reacting the same with ketene.

Description

Process for the preparation of 1, 3,5-triacetyl-2, 4-dioxohexahyd.ro-1, 3, 5-triazine

The invention relates to a process for obtaining pure 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (hereinafter TADHT for short) and to processes for the preparation of TADHT from 2,4-dioxohexahydro-1 , 3, 5-triazine (hereinafter simply DHT), 1-acetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (hereinafter MADHT short) or from 1, 5-diacetyl-2, 4-dioxohexahydro -l, 3, 5-triazine (hereinafter DADHT) by reaction with ketene and the subsequent recovery of pure TADHT.

TADHT DADHT MADHT DHT

DADHT was first prepared and described synthetically in studies on nucleic acid chemistry in 1962, and its use as a bleach activator in detergents is known in the art (Beckhaus et al., Chem. Techn. 1988, 40, 423, DD 219034).

Bleach activators are used in detergents to activate bleaches in detergent compositions even at low temperatures. That in Europe as a bleaching agent Mainly used sodium perborate hydrolyzed in aqueous solution to form hydrogen peroxide. In the alkaline wash, hydrogen peroxide is converted to the bleach-active perhydroxyl anion, the concentration increasing with temperature and pH. Bleach activators are compounds whose use is based on the fact that they form organic peracids in the alkaline medium with hydrogen peroxide, which have a higher oxidation potential than hydrogen peroxide and cause activation of the bleaching action of sodium perborate in the lower temperature range. The currently most commonly used bleach activator is likely to be tetraacetylenediamine (TAED).

DADHT has the advantage that all acetyl groups are available, whereas in TAED only 2 of 4 acetyl groups can react.

Beckhaus et al. report that the preparation of the 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) can only be achieved by acetylation of DADHT with ketene.

DADHT is named after Beckhaus et al. by acetylation of DHT, with reactive acetylating reagents such as acetic anhydride, acetyl chloride and ketene. Such a method is also the subject of DD 229696 A1.

In DD 229696 A1, the disadvantage of handling gaseous toxic ketene and its tendency to dimerization is emphasized with respect to the acetylation with ketene, so that acetylation of DHT to DADHT by means of sulfuric acid / acetic anhydride is described as advantageous. DD 229696 Al, however, contains no disclosure of how to represent TADHT. Fundamentally problematic in the acetylation of DHT to DADHT by means of sulfuric acid / acetic anhydride is the fact that both DHT and DADHT is only slightly soluble in acetic anhydride and DADHT further has only a low solubility in the acetic acid by-produced in the acetylation. Furthermore, it should be noted that impurities of technical DHT, such as urea, biuret and methylene diurea, under the conditions mentioned also in the corresponding

Diacetyl derivatives are converted. Also, the acid used as catalyst can react with the acetic anhydride. Only the cyanuric acid contained in the DHT undergoes acetylation as an inert substance.

For a complication-free separation of the DADHT from the acetylation a practically quantitative conversion of DHT is required. In contrast to the DADHT, the acetylated by-products of the DHT preferentially remain in solution, while the cyanuric acid over the solid and liquid

Reaction products distributed. However, technical grade DADHT still contains up to 7.0% by weight of cyanuric acid and still 0.5% by weight of DHT.

For the production of DHT, in turn, alternative methods are known from the prior art, but one

Possibility represents the condensation of urea and formaldehyde. Such a method is also described in EP 0186022 A1. Technically produced DHT still contains up to 9.9 wt.% Cyanuric acid, as well as small amounts of urea and biuret. Another acetylation product of DHT is the monoacetylated 1-acetyl-2,4-dioxohexahydro-1,3,5-triazine (MADHT), the selective synthesis of which has not previously been described in the prior art. MADHT reacts very easily to the DADHT in the acetylation of DHT.

Technical MADHT can be obtained by partial acetylation of DHT with acetic anhydride under preferably mild acetylation conditions or conversely by partial hydrolysis of DADHT and TADHT.

In the prior art, no method has been described, which offers a large-scale access to the production of sufficiently pure 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (TADHT). In particular, no method has yet been described in the prior art, such as TADHT directly from

DHT or by the implementation of DADHT and / or MADHT on an industrial scale in great purity is accessible.

TADHT is also from Klepp et al. and was characterized only by an X-ray structure analysis (K.O. Klepp, M. Stähr, H. Schmidt, Journal of Crystallography - New Crystal Structures 2000, 215, 151). Klepp et al. also describe only that TADHT was obtained by reacting DADHT with ketene in acetic anhydride without giving further details.

The problem with the production of TADHT is that the use of the technical starting products DADHT, MADHT and DHT, in turn, lead to impurities which are difficult to separate from the TADHT-containing reaction mixtures because of the impurities contained therein. So you get, if you for example, DADHT after Klepp et al. reacts with ketene in acetic anhydride, only a heavily contaminated product: If DADHT is allowed to react with ketene in acetic anhydride, so after removal of the solvent in vacuo, a solid brown-black paste with 1.5 to 4.0 times

Mass of the inserted DADHT. In addition to TADHT, DADHT and DHT, MADHT, cyanuric acid and other impurities can also be detected in this product which, as a result of the preparation, were already present in the DADHT employed or formed during the reaction. A technically simple and inexpensive to be realized workup of this practically useless reaction mixture, which leads to high yields of TADHT, however, is not known from the prior art. Without such a process, however, an economic exploitation of the interesting TADHT is excluded.

It was therefore an object to provide a method that allows large-scale access to TADHT in high purity. In particular, the object was to provide a method that the isolation and complete removal of TADHT (1, 3, 5-triacetyl-2, 4-dioxohexahydro-1, 3, 5-triazine) of the impurities from various reaction masses for Making TADHT possible.

The task was solved by observing various parameters during production and a new work-up procedure of TADHT-containing reaction mixtures. The invention relates to a process for obtaining 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (TADHT), comprising the following steps

a) separation of the optionally insoluble fractions from a solution containing 1, 3, 5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine in a polar aprotic solvent,

b) concentration of the resulting solution and separation of the resulting precipitate and

c) optional recrystallization of the precipitate from a polar aprotic solvent.

By the workup process according to the invention, the precursors from the production of TADHT contained in the reaction mixture such as DHT, DADHT, MADHT and typical impurities such as cyanuric acid are separated and TADHT in high purity (usually more than 97% pure).

The recrystallization in step c) can be carried out from the same or from a different solvent than the solvent used in step a). When step c) is carried out, the recrystallization is preferably carried out from another solvent.

The solution of 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) in a polar aprotic solvent can be obtained by taking up a crude product of TADHT obtained by any method in such a way or preferably directly corresponding to the resulting reaction mixture from the preparation of TADHT. The work-up process according to the invention can thus be described as downstream Step to the preparation of TADHT in a polar aprotic solvent. This preparation may in particular be the synthesis of TADHT in a polar aprotic solvent from DHT with ketene or from DADHT with ketene (cf also see below).

When the solution of 1, 3, 5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) directly corresponds to the reaction mixture obtained from the production of TADHT, in particular from a preparation of TADHT from DHT with ketene, from DADHT with ketene or from MADHT with ketene, so the separated in step a) insoluble fraction in the polar aprotic solvent usually - in addition to other impurities - still certain amounts of MADHT and DADHT. In a preferred embodiment of the process according to the invention, in such a case the separated insoluble fraction is again used or mixed in as educt for the production of TADHT, in order to achieve a complete acetylation of the MADHT to the TADHT and thus to achieve maximum raw material utilization. Accordingly, a preferred embodiment consists in the recycling of the insoluble fractions separated in step a) into a TADHT production process starting from DHT, DADHT or MADHT, preferably into a preparation process in which ketene is used as acetylating reagent.

From the state of the art, no work-up procedures have hitherto been known, such as TADHT can be isolated from the crude reaction mixtures, in particular from reaction mixtures which result from the production of TADHT from DADHT with ketene, with high yields and high purity.

The process according to the invention makes it possible to isolate pure TADHT in high yield by using aprotic solvents. In order to achieve high purities of TADHT, the solvent or the solvent mixture used for unreacted reactants and impurities must have the best possible solubility. In order to achieve high yields of TADHT this should have only the lowest possible solubility in it.

Polar solvents would be suitable for this purpose, but preferred are polar aprotic solvents, since these do not have any undesirable side reactions with the as

Acetylation reagent Keten enter into, the TADHT-containing solution should directly originate from a manufacturing process for TADHT. Particularly preferred are commercially available, inexpensive recyclable solvents.

Typical polar aprotic solvents for the solution containing TADHT can be selected from the solvents commonly used for the production of TADHT. In particular, solvents selected from the group comprising ketones (such as, for example, acetone and methyl ethyl ketone (MEK)), acetic anhydride (ESA) and dimethyl sulfoxide (DMSO) and / or mixtures thereof are suitable.

In particular, when the TADHT-containing solution does not directly derive from a production process for TADHT, aprotic polar solvents are selected from the group consisting of ketones (such as acetone and methyl ethyl ketone (MEK)), esters (such as methyl acetate, ethyl acetate and butyl acetate) and ethers (such as 1, 2-dimethoxyethane and tetrahydrofuran (THF)) and / or mixtures thereof. The aforementioned However, solvents are also generally used in the recrystallization.

In any case, insoluble fractions (soil or precipitate) present in the solution containing 1, 3, 5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) are removed in a first step, preferably by filtration , Decantation or centrifugation are possible, for example. Optionally, the separated insoluble fractions can be recycled to a TADHT manufacturing process to achieve maximum recovery of raw material.

Concentration of the solution by distillation, optionally at elevated temperature and / or reduced pressure, reduces the amount of solvent. The precipitating solid

(Precipitate) may optionally be from the same or from another polar aprotic solvent or

Recrystallized solvent mixture. The solid which precipitates on concentration or the solid obtained from the optional recrystallization contains TADHT in high purity. In the case of large-scale implementation, complete removal of the solvent during concentration is generally dispensed with and the solvent used if appropriate for recrystallization is added before reaching complete dryness.

The solvent used for recrystallization is particularly preferably selected from the group consisting of acetone, ethyl acetate and 1, 2-dimethoxyethane. In particular, acetone is suitable. So can acetone already for the

Representation of the TADHT, in particular for the presentation of TADHT from DHT, MADHT or DADHT using ketene, used become. After separation of the insoluble constituents from the reaction mixture containing TADHT and concentrating the solution, the product can generally be isolated from acetone without further recrystallization in high purity and yield.

In another preferred possible embodiment of the work-up method according to the invention TADHT is in acetic anhydride (ESA) - produced as the first polar aprotic solvent - from DADHT or DHT using ketene and then re-crystallization another aprotic

Solvent used, in particular acetone. Thus, after the separation of the insoluble in acetic anhydride components and concentration, the subsequent recrystallization from acetone. Also, a recrystallization from 1, 2-dimethoxyethane or ethyl acetate instead of acetone is particularly preferred.

The amount of solvent in recrystallization is generally chosen so that the amount of TADHT contained is dissolved in the heat, but precipitates in the cold, the impurities should remain as possible in solution. Preferred amounts of solvent are present when TADHT is present in a dissolved state at or in the immediate vicinity of the boiling point. The crystallization can be carried out by adding a polarity in the direction of unpolar solvent or by cooling the solution to suitable temperatures below the boiling point, preferably to a temperature between -20 ⁰ C to + 50 ⁰ C, more preferably at 0 ° C to 20 ⁰ C. respectively. For ease of implementation, all working steps at ambient pressure and atmosphere are preferred, although the variation of these parameters is possible. The 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (TADHT) containing solution in an aprotic solvent is preferably the reaction solution in which the TADHT was prepared, ie the process product of a TADHT production process.

In a possible embodiment of the work-up process according to the invention, the TADHT-containing solution from which insoluble constituents present in step a) are removed is the reaction mixture which is produced in the preparation of TADHT from DADHT or MADHT, preferably from DADHT by acetylation with ketene in acetic anhydride ( ESA).

In a further possible embodiment of the work-up process according to the invention, the TADHT-containing solution from which any insoluble constituents present in step a) are removed, is the reaction mixture which is produced in the preparation of TADHT from DHT by acetylation with ketene in a polar aprotic solvent inert to ketene , especially

Acetic anhydride (ESA), dimethyl sulfoxide (DMSO) or acetone is obtained.

As long as the separated insoluble constituents still contain significant amounts of mono- (MADHT) or diacetylated (DADHT) products, these are again fed to a TADHT production process as starting material.

As in technical DADHT, a possible educt for the

Production of TADHT, this only a content of about 93 It was surprising that the simultaneous removal of formed by-products, unreacted by-products from DADHT, and strongly colored components was achieved by the use of polar aprotic solvents.

Another object of the invention is the direct production of TADHT from DHT, which has not yet been described in the prior art.

Thus, a further subject of the invention is a process for preparing 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) by reacting 2,4-dioxohexahydro-1,3,5 - triazine (DHT) in a ketene-inert solvent with ketene.

The reaction mixture obtained after the reaction can then be subjected directly to the work-up procedure of the invention described above.

A possible embodiment is therefore a process for preparing 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) containing the following steps

a) reaction of 2,4-dioxohexahydro-1,3,5-triazine (DHT) with ketene in a polar aprotic solvent,

b) separation of the optionally insoluble fractions from the reaction mixture containing a solution of 1, 3, 5-triacetyl

2, 4-dioxohexahydro-l, 3, 5-triazine (TADHT) in a polar aprotic solvent

c) concentration of the resulting solution and separation of the resulting precipitate and d) optional recrystallization of the precipitate from a polar aprotic solvent.

The production process of TADHT according to the invention from DHT can in principle be carried out in the presence or absence of acetic anhydride.

The insoluble constituents separated off in step b) can in turn be fed to a TADHT production process in order to achieve maximum raw material yield.

In particular, acetic anhydride (ESA), dimethyl sulfoxide (DMSO) and acetone are suitable as inert polar aprotic solvents with respect to ketene, most preferably acetic anhydride.

The process according to the invention can also be carried out in DMSO or acetone. Acetone as a solvent offers the advantage that the desired product TADHT can be crystallized or recrystallized directly from the reaction solution after separation of the impurities in the form of the forming body (precipitate), in particular by filtration, ie the reaction solution containing the TADHT forming precipitate is usually recrystallized from any other aprotic solvent.

The advantage of DMSO as a solvent for acetylation is that in DMSO the solubility of DHT is relatively high at 2% by weight at 20 ^° C. The reaction is preferably carried out in a temperature range of 0-80 ⁰ C, preferably between 20-60 ⁰ C, most preferably between 30 - 40 ° C. The educt DHT is usually present as a suspension in the solvent, which is polar enough to dissolve at least a small amount of DHT, is introduced into the gaseous ketene. During the ketene initiation both the temperature and the ketene amount should be controlled, because if one or both parameters are chosen too large, it can lead to a strong discoloration of the reaction mass due to intense

By-product formation occur and the isolation of the illustrated TADHT is considerably more difficult.

The amounts of ketene used for complete conversion of DHT to TADHT are generally 3.0 to 4.0, preferably 3.0 to 3.4, mol equivalents based on the DHT used.

Optionally, a catalyst can be used, but is preferably dispensed with the addition of a catalyst. When catalysts are used, acidic catalysts are preferred, in particular sulfoacetic acid and / or acetic acid.

In a preferred embodiment of the production process according to the invention for TADHT from DHT, a further reaction is carried out after complete addition of the ketene. The post-reaction time is preferably 0.5 to 7 hours, preferably in particular 1 to 3 hours in the specified temperature range. In this way, in addition to a completion of the reaction optionally acylatable by-products and / or Losemittelbestandteile be acylated. This one-step production method for TADHT directly from DHT avoids the cumbersome two-step process known from the prior art (conversion of DHT with acetic anhydride to DADHT and its subsequent reaction with ketene to TADHT) and uses ketene as the actual acetylating agent. Optionally, acetic acid formed during the process is converted back into acetic anhydride.

Due to the extremely poor solubility of DHT in

Acetic anhydride at room temperature (<0.02%) DADHT is prepared from the known from the prior art method at 90 - 110 ⁰ C. Also due to the high reaction temperature, the purity of the technical product DADHT thus produced is generally only about 85%. It was therefore very surprising that the direct preparation with ketene as acetylating even at low temperature leads to a good turnover in a short time and that can be such high purity TADHT win in high yield.

The reaction mixture obtained by the acetylation of DHT to TADHT by means of ketene can then be directly subjected to the abovementioned work-up procedure according to the invention, in which case the insoluble constituents which are optionally present are first separated off and the remaining solution is concentrated. Depending on the solvent used for the acetylation can then optionally recrystallization from another aprotic solvent, in particular from the above-mentioned preferred solvents, take place. This gives pure TADHT (usually around 98%) as a white solid in high yield (usually 80-90%). The initially separated insoluble constituents usually still contain significant amounts of acetylatable precursors, in particular MADHT, so that they can be used again as educt for acetylation with ketene.

Another object of the invention is the preparation of TADHT from DADHT and / or MADHT followed by the work-up method according to the invention.

It is known from the prior art that TADHT can be obtained from DADHT by means of ketene in acetic anhydride, but not as can be obtained industrially and with high yields and purities of TADHT, in particular such a reaction mixture is economically worked up.

In the prior art, no process for the preparation of TADHT from MADHT or MADHT and DADHT-containing mixtures has been described.

Thus, another object of the invention is a process for the preparation of 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (TADHT), comprising the following steps

a) reaction of 1, 5-diacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (DADHT) and / or 1-acetyl-2,4-dioxohexahydro-l, 3, 5-triazine (MADHT) with Ketene in acetic anhydride,

b) separation of the optionally insoluble fractions from the reaction mixture comprising a solution of 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine (TADHT) in acetic anhydride,

c) concentration of the resulting solution and separation of the resulting precipitate and

d) optional recrystallization of the precipitate from a polar aprotic solvent. The recrystallization in step d) can be carried out from the same or from a different solvent than the solvent used in step a) or b). When step d) is carried out, the recrystallization is preferably carried out from another solvent.

Preferably, the inventive method is carried out starting from 1, 5-diacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (DADHT) or predominantly containing DADHT mixtures as starting material in step a).

Characteristic of the process according to the invention is that the reaction mixture obtained from the acetylation with ketene already contains the TADHT, first the insoluble ones

Components (soil or precipitate) are separated. This separation is again preferably carried out by filtration. Only by the separation of the insoluble constituents, then pure TADHT can be isolated. The separated components can then - as described above several times - again perform a TADHT production process as starting material. The acetic anhydride solution containing TADHT obtained after this separation is then concentrated and the resulting precipitate is isolated and preferably recrystallized again from another aprotic polar solvent, in particular from a preferred solvent mentioned above.

The solvent used for recrystallization is particularly preferably selected from the group consisting of acetone, ethyl acetate and 1, 2-dimethoxyethane. In particular, acetone is suitable. In one possible embodiment of the process according to the invention, a suspension of DADHT and / or MADHT in acetic anhydride is reacted with ketene. The amount of acetic anhydride is at least so large that it is capable of safely removing the heat of reaction. Preference is given to an amount which completely or partially holds DADHT and / or MADHT in solution and gives a workable reaction mass, particularly preferably 5 to 40 times the excess of the DADHT and / or MADHT composition.

To achieve the fullest possible conversion, a stoichiometric amount or an excess of ketene based on the DADHT and / or MADHT used is generally used. Preferably, an excess of ketene is introduced into the reaction mixture (suspension). However, too much ketene can lead to a dark colored product. As a rule, a 1.5-3.5-fold excess of ketene is used based on the DADHT and / or MADHT used.

The reaction (acetylation) is usually carried out at 0 - 80 ⁰ C, preferably at 30 - 40 ⁰ C.

After completion of the introduction of the ketene, a post-reaction is preferably carried out with stirring, usually 0 - 10 h, more preferably for 1 - 3 h. Subsequently, the remaining solid (usually DHT, cyanuric acid and other not readily identified difficult to get rid of

Impurities) separated, preferably filtered off. Only in this way can very pure TADHT be obtained. Thereafter, from the reaction solution, acetic anhydride, (z. B. 60 ⁰ C), especially at elevated temperature and reduced pressure (eg., 10 mbar), distilled off and the residue obtained is diluted with acetone or added, heated to boiling and then slowly cooled (eg to 0 ⁰ C), wherein a solid precipitates. After filtering off the precipitated solid and washing with Acetone, preferably cooled acetone, gives about 90% TADHT as a white solid.

It is possible with a simple method to acetylate DADHT and / or MADHT and thus produce TADHT in high yield and purity, which is particularly surprising since the isolation of a product in pure form from a material that is less soluble or contains less soluble impurities, is usually problematic, since only products with poor purity can be obtained in the usual way.

The implementation of all processes described consisting of the generation and metering of reaction mass and solvent (s), temperature control and generation and removal of the crystals can be carried out partially or completely continuously or discontinuously. During the entire implementation of the invention

Manufacturing process for TADHT the used and / or formed solids are dissolved only to a small extent. Also at the end of the reaction are solids in the form of unreacted starting materials, by-products and / or intermediates. In order to achieve the fullest possible conversion or degree of acylation, it is advantageous to intensively mix the reaction mass, which in addition to a batch reactor operated batchwise also a usually smaller volume tubular or loop reactor is suitable in the educt and / or product streams continuously on or be discharged.

As starting material for carrying out the work-up process according to the invention for the production of pure TADHT, in particular reaction masses are suitable, which are based on an above described method for the preparation of TADHT from DHT, DADHT and / or MADHT were obtained.

In a preferred embodiment of the work-up process according to the invention for the production of pure TADHT, which is also followed by the production process according to the invention of TADHT from DHT, DADHT and / or MADHT, the insoluble fractions of 1,3 and 3 obtained in steps a) and b) are separated , 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine (TADHT) containing solution in a polar aprotic

Solvent or acetic anhydride used again as starting material for the production of TADHT and reused and thus achieved a maximum raw material yield.

The following examples are given to illustrate the invention in detail and are in no way to be considered as limiting.

Examples

Example 1 - Preparation of TADHT from DADHT with ketene in acetic anhydride, work-up with acetone

30 g of DADHT (solid) (0.15 mol) are initially charged at room temperature in a three-necked flask with magnetic stirrer, reflux condenser, thermometer, ketene inlet tube, 400 g

Acetic anhydride (ESA) is added, the reverse addition is also possible. The white suspension is heated to 30 ⁰ C and introduced keten at 30 ⁰ C at 5 g / h (slightly exothermic reaction). When the formulation adopts an olive green color, the ketene dosage is terminated to prevent deterioration of color properties. A total of 19.4 g of ketene (0.46 mol) was introduced, whereby losses were compensated by outgassed ketene. Then it will be

Stirred for 1 - 3 h at RT, wherein solid clumps together and precipitates. The solid is sucked off via a suction filter. There are obtained 2.2 g of a white-gray solid. After ¹ H NMR, the solid contains DHT and other impurities. The filtrate is then concentrated on a rotary evaporator at up to 60 ⁰ C and 10 mbar and added to the light dark gray residue (44.2 g) 240 ml of acetone and the suspension for 60 min. Boiled. The result is a dark brown solution which is slowly cooled to RT and then further to 0 ⁰ C. The beige suspension obtained is filtered off with suction filter, the solid washed twice with 40 ml of chilled acetone and dried in vacuo at 60 ° C. There are obtained 32.0 g of TADHT (0.13 mol, yield 88%). The HPLC analysis showed a content of 98.6%. ¹ H NMR (d ₆ -DMSO): 2.42 ppm (6H), 2.54 ppm (3H), 5.55 ppm (2H). Melting point: 169 ° C.

Example 2 - Preparation of TADHT from DADHT with ketene in acetic anhydride, work-up with ethyl acetate Analogously to Example 1, but ethyl acetate is used instead of acetone (82% yield, 97.6% content, melting point 168 ° C).

Example 3 - Preparation of TADHT from DADHT with ketene in acetic anhydride, work-up with dimethoxyethane

Analogously to Example 1, but instead of acetone, 1,2-dimethoxyethane (DME) is used (80% yield, 97.0% content, melting point 167 ° C.).

Example 4 - Preparation of TADHT from DHT with ketene in acetic anhydride, working up with acetone

15 g of DHT (solid) (0.13 mol) are suspended at room temperature in a three-necked flask with magnetic stirrer, reflux condenser, thermometer, Keteneinleitrohr in 400 g of ESA. The white suspension is heated to 30 ⁰ C and introduced keten at 30 - 40 ⁰ C at 10 g / h (exothermic reaction). If the mixture warms up or turns very dark, the dosing rate of ketene must be reduced. When the batch finally assumes an olive-green color, the ketene dosage is stopped to prevent deterioration of the

To prevent color properties. A total of 18.7 g of ketene (0.44 mol) was introduced, which also compensated for losses by outgassed ketene. Then it will be

Stirred for 1 - 3 h at RT, wherein solid clumps together and precipitates. The solid is sucked off via a suction filter. There are obtained 2.1 g of a white-gray solid. After ¹ H NMR, the solid contains DHT, DADHT and other impurities. The filtrate is then concentrated on a rotary evaporator at up to 60 ⁰ C and 10 mbar and added to the light dark gray residue (45.2 g) of 250 ml of acetone and the suspension for 60 min. Boiled. The result is a dark brown solution, which is slowly cooled to RT and then further to 0 ⁰ C. The beige suspension obtained is over a Suction filtered, the solid washed twice with 30 ml of chilled acetone and dried in vacuo at 60 ⁰ C. There are obtained 26.1 g of TADHT (0.11 mol, yield 83%). The HPLC analysis showed a content of 97.4%. ¹ H NMR (d ₆ -DMSO): 2.42 ppm (6H), 2.54 ppm (3H), 5.55 ppm (2H). Melting point: 170 ^° C.

Example 5 - Preparation of TADHT from DHT with Ketene in Dimethylsulfoxide, Work-Up with Ethyl Acetate 15 g of DHT (solid) (0.13 mol) are suspended at room temperature in 400 g of dimethyl sulfoxide (DMSO) in a three-necked flask with magnetic stirrer, reflux condenser, thermometer, ketene inlet tube , The white suspension is heated to 30 ⁰ C and introduced keten at 30 - 50 ⁰ C at 10 g / h (exothermic reaction). If the batch warms up or turns very dark, the metering rate of the ketene must be throttled or temporarily stopped. When the formulation finally assumes a dark, olive-green color, the ketene dosage is terminated to prevent deterioration of color properties. A total of 19.3 g of ketene (0.46 mol) was introduced, whereby losses were compensated by outgassed ketene. The mixture is then stirred for 1 - 3 h at RT, wherein the initially finely divided solid clumps together and precipitates. This solid is filtered off with suction. There are obtained 2.4 g of a grayish solid. After ¹ H NMR, the solid contains DHT, DADHT and other impurities. The filtrate is concentrated on a rotary evaporator at up to 100 ⁰ C and about 3 mbar and added to the light dark gray residue (55.2 g) of 300 ml of ethyl acetate and the suspension heated to boiling for 60 min. The result is a dark brown solution, which is gradually cooled to 0 ⁰ C is. The resulting beige suspension is filtered off with suction, the solid washed twice with 30 ml of cooled ethyl acetate and dried at 60 ⁰ C in vacuo. It 22.4 g of TADHT are obtained (0.09 mol, yield 71%). The HPLC analysis showed a content of 97.2%. ¹ H NMR (d ₆ -DMSO): 2.42 ppm (6H), 2.54 ppm (3H), 5.55 ppm (2H). Melting point: 167 ° C.

Example 6 - Preparation of TADHT from DHT with ketene in acetone, work-up with dimethoxyethane

15 g of DHT (solid) (0.13 mol) are suspended at room temperature in a three-necked flask with magnetic stirrer, reflux condenser, thermometer, Keteneinleitrohr in 850 g of acetone. The white suspension is heated to 30 ⁰ C and introduced keten at 30 - 50 ⁰ C at 10 g / h (exothermic reaction). If the mixture warms up or turns very dark, the dosing rate of ketene must be temporarily reduced. When the formulation finally assumes an olive-green color, the ketene dosage is terminated to prevent deterioration of color properties. A total of 15.7 g of ketene (0.37 mol) was introduced, whereby losses were compensated by outgassed ketene. The mixture is then stirred for 1 - 3 h at RT, wherein solid clumps together and precipitates when stopping the stirrer. The solid is sucked off via a suction filter. There are obtained 2.8 g of a white-gray solid. After ¹ H NMR, the solid contains DHT, DADHT and other impurities. The filtrate is then concentrated on a rotary evaporator at up to 60 ⁰ C and 10 mbar and added to the light dark gray residue (45.2 g) 400 ml of 1,2-dimethoxyethane and the suspension for 20 min. Boiled. The result is a dark brown solution, which is cooled slowly to RT and then further to 0 ⁰ C. The beige suspension is filtered off with suction filter, the solid washed twice with 50 ml of cooled 1, 2-dimethoxyethane and at 60 ⁰ C im Vacuum dried. There are obtained 24.2 g of TADHT (0.10 mol, yield 77%). HPLC analysis gave a content of 97.2%. ¹ H NMR (d ₆ -DMSO): 2.42 ppm (6H), 2.54 ppm (3H), 5.55 ppm (2H). Melting point: 168 ° C.

Example 7 - Preparation of TADHT from DHT with ketene in acetone, working up with acetone

15 g of DHT (solid) (0.13 mol) are suspended at room temperature in a three-necked flask with magnetic stirrer, reflux condenser, thermometer, Keteneinleitrohr in 1000 g of acetone. In the white suspension is introduced at 20 ⁰ C ketene initially 10 g / h. In the exothermic reaction, the heated

Suspension, which is held by initially only cooling, later cooling and throttling the Ketenzufuhr to 40 - 50 ⁰ C. If the mixture turns very dark, the dose of ketene must be temporarily adjusted. When the formulation finally assumes an olive-green color, the ketene dosage is terminated to prevent deterioration of color properties. In total, an amount of 22.7 g of ketene (0.54 mol) was introduced, which also compensated for losses from outgassed ketene. The mixture is then stirred for 1 - 3 h at RT, wherein solid clumps together and precipitates when stopping the stirrer. The solid is sucked off via a suction filter. There are obtained 2.8 g of a gray-green solid. After ¹ H NMR, the solid contains DHT, DADHT and other impurities. The filtrate is concentrated on a rotary evaporator at up to 40 ⁰ C and about 10 mbar to a final volume of 250 ml and the suspension for 30 min. heated to boiling. The result is a dark brown solution which is slowly cooled to RT and then further to 0 ⁰ C. The beige suspension is filtered off with suction filter, the solid washed twice with 30 ml of chilled acetone and dried at 60 ⁰ C in vacuo. There are obtained 25.6 g of TADHT ((0.12 mol) yield 81%). HPLC analysis showed a content of 98.2%. ¹ H NMR (d ₆ -DMSO): 2.42 ppm (6H), 2.54 ppm (3H), 5.55 ppm (2H). Melting point: 169 ° C. Example 8 - Preparation of TADHT from recycled solid with ketene in acetic anhydride, working up with acetone

30 g of the obtained in the workup of the above-described mixtures and separated solid (maximum 0.15 mol or 0.26 mol, if calculated as DADHT or DHT, in addition to these two reactants also contains MADHT and other impurities) are at room temperature in a three-necked flask with magnetic stirrer, reflux condenser, thermometer, Keteneinleitrohr submitted, 400 g of acetic anhydride (ESA) was added, the reverse addition is also possible. The green-brown suspension is heated to 30 ⁰ C and introduced keten at 30 - 50 ⁰ C at 10 g / h (slightly exothermic reaction). When the formulation takes on a deep, dark brown color, the ketene dosage is terminated to prevent further deterioration of color properties. Total was 22.3 g of ketene

(0.53 mol), whereby losses were compensated by outgassed ketene. The mixture is then stirred for 1 - 3 h at RT, wherein solid clumps together and precipitates. The solid is sucked off via a suction filter. There are obtained 4.2 g of a white-gray solid. After ¹ H NMR, the solid contains DHT, MADHT and other impurities. The filtrate is then concentrated on a rotary evaporator at up to 60 ⁰ C and 10 mbar and added to the brown residue (54.8 g) 280 ml of acetone and the suspension for 60 min. Boiled. The result is a dark brown solution which is slowly cooled to RT and then further to 0 ⁰ C. The beige suspension obtained is filtered off with suction filter, the solid washed twice with 40 ml of chilled acetone and dried in vacuo at 60 ° C. There are obtained 28.6 g of TADHT (0.12 mol, yield 45-79% based on DHT or DADHT). HPLC analysis showed a content of 97.2%. ¹ H NMR (d ₆ -DMSO): 2.42 ppm (6H), 2.54 ppm (3H), 5.55 ppm (2H). Melting point: 167 ° C.

Claims

Claims:

A process for recovering 1, 3, 5-triacetyl-2, 4-dioxohexahydro-1,3,5-triazine, comprising the following steps

a) separation of the optionally insoluble fractions from a solution containing 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine in a polar aprotic solvent

c) optional recrystallization of the precipitate from a polar aprotic solvent.

2. The method according to claim 1, characterized in that polar aprotic solvents selected from the group containing ketones, esters, ethers, acetic anhydride and dimethyl sulfoxide or mixtures thereof are used.

3. The method according to claim 1, characterized in that polar aprotic solvents selected from the group comprising acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, butyl acetate, 1, 2-dimethoxyethane, tetrahydrofuran, acetic anhydride and dimethyl sulfoxide or mixtures thereof are used.

4. The method according to claim 1, characterized in that in step a) a solvent selected from the group comprising acetone, dimethyl sulfoxide and acetic anhydride or mixtures thereof and in step c) a solvent selected from the group consisting of acetone, methyl ethyl ketone, methyl acetate, ethyl acetate butyl acetate , 1, 2-dimethoxyethane, tetrahydrofuran or mixtures thereof.

5. The method according to claim 1, characterized in that a polar aprotic solvent selected from the group containing acetone, ethyl acetate and 1, 2-dimethoxyethane is used.

6. The method according to one or more of claims 1 to 5, characterized in that the 1, 3, 5-triacetyl-2, 4-dioxohexahydro-1, 3, 5-triazine-containing solution, from the in step a) optionally present insoluble constituents are separated off, a reaction mixture which, in the preparation of 1, 3, 5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine from 1,5-diacetyl-2,4-dioxohexahydro-1, 3, 5-triazine is obtained by acetylation with ketene in acetic anhydride.

7. The method according to one or more of claims 1 to 5, characterized in that the 1, 3, 5-triacetyl-2, 4-dioxohexahydro-1, 3, 5-triazine-containing solution, from the in step a) optionally present insoluble constituents are separated, the reaction mixture which, in the preparation of 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine from 2, 4-Dioxohexahydro-l, 3, 5-triazine means Acetylation with ketene in a ketene-inert polar aprotic solvent is obtained.

8. A process for the preparation of 1, 3, 5-triacetyl-2, 4-dioxohexahydro-1, 3, 5-triazine by means of the reaction of 2,4-dioxohexahydro-1, 3, 5-triazine with ketene in a ketene inert towards Solvent.

9. The method according to claim 8 for the preparation of 1,3,5-

Triacetyl-2,4-dioxohexahydro-1,3,5-triazine containing the following steps

a) reaction of 2,4-dioxohexahydro-1,3,5-triazine with ketene in a polar aprotic solvent,

b) separation of the optionally insoluble fractions from the reaction mixture containing a solution of 1, 3, 5-triacetyl 2, 4-dioxohexahydro-l, 3, 5-triazine in a polar aprotic solvent

d) optional recrystallization of the precipitate from a polar aprotic solvent.

10. A process for the preparation of 1, 3, 5-triacetyl-2, 4-dioxohexahydro-1, 3, 5-triazine, comprising the following steps

a) reaction of 1, 5-diacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine and / or 1-acetyl-2,4-dioxohexahydro-l, 3, 5-triazine with ketene in

acetic anhydride,

b) separation of the optionally insoluble fractions from the reaction mixture comprising a solution of 1,3,5-triacetyl-2,4-dioxohexahydro-1,3,5-triazine in acetic anhydride,

d) optional recrystallization of the precipitate from a polar aprotic solvent.

11. The method according to claim 10, characterized in that in step a) 1, 5-diacetyl-2, 4-dioxohexahydro-l, 3, 5-triazine or an educt predominantly containing 1, 5-diacetyl-2, 4 dioxohexahydro 1, 3, 5-triazine is used.

12. The method of claim 1, 9 or 10, characterized in that in step a) or step b) first separated insoluble constituents in a process for the preparation of 1, 3, 5-triacetyl-2, 4-dioxohexahydro-l , 3, 5-triazine can be recycled as starting material.