EP1100784A1

EP1100784A1 - Method for the production of n,n'-carbonyl diazoles

Info

Publication number: EP1100784A1
Application number: EP99936551A
Authority: EP
Inventors: Johannes Scherer; Alexander Klausener; Robert Söllner
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1998-07-28
Filing date: 1999-07-16
Publication date: 2001-05-23
Also published as: HUP0103373A3; US6392057B1; HUP0103373A2; CA2338631A1; PL345697A1; CN1311781A; JP2002521474A; HK1040079A1; AU5160599A; WO2000006551A1; IL140529A0; KR20010072086A; DE19833913A1

Abstract

The invention concerns a method for the production of N,N'-carbonyl diazoles by reacting azoles with phosgene in a solvent, wherein the azole and the phosgene are introduced into an aromatic solvent dehydrated by distillation at a doses such that 1 mol azole is introduced at the same time as 01.17 to 0.34 mol of phosgene is dosed. The invention also describes special advantageous possibilities for processing the reaction mixture.

Description

Process for the preparation of N, N'-carbonyidiazoles

The present invention relates to an improved process for the preparation of N, N'-carbonyldiazoles by reacting azoles with phosgene.

It is already known that N, N'-carbonyldiazoles can be obtained if azoles are reacted with phosgene (see DE-AS 10 33 210). Tetrahydrofuran, other ethers and hydrocarbons are proposed as solvents, in particular anhydrous tetrahydrofuran and mixtures of

Tetrahydrofuran with benzene (see Chem. Ber. 96, 3374 (1963) and Org. Synth. Coll. Vol. IV, 201-204 (1968)). The reaction is obviously carried out at room temperature, phosgene being introduced into a solution of the azoles. For this process, the last traces of water must be removed from the solvent. Since this is dealing with metallic sodium, sodium hydride or

Calcium hydride requires, this means the use of extraordinary safety measures for working on a technical scale. In addition, there is always a risk of formation of explosive peroxides with tetrahydrofuran and other ethers. In addition, the process is difficult to reproduce.

According to a newer process (EP-A2 692 476), these problems are avoided by working in an aromatic solvent such as benzene, toluene or chlorobenzene, which has been dehydrated by distillation, at temperatures from 50 to 120 ° C. In practice, one proceeds by first passing the solvent through

Distillation dehydrated, then introducing the azole, dissolving it with heating and then introducing phosgene.

However, the method of introducing phosgene into the azole solutions presented has the following disadvantages: If one works at temperatures below 50 ° C., solvents such as tetrahydrofuran, which is problematic for the reasons mentioned above, must be used, since the solubilities of both the azoles and the carbonyldiazoles in the solvents which are easier to dry and do not tend to form peroxides, such as benzene, toluene, Xylenes or monochlorobenzene are too low.

If one works at temperatures above 50 ° C., the azole hydrochloride precipitate formed during the reaction accumulates as a viscous, sticky mass which adheres firmly to the vessel wall and stirrer, making it very difficult to stir. The stiffness of stirring then limits the maximum possible space yield to relatively low values. When the precipitate solidifies towards the end of the phosgene addition, hard balls are formed which can cause damage to the reaction vessel and its internals (e.g. stirrers, immersion tubes, etc.).

There is therefore still a need for a process for the preparation of N, N'-carbonyldiazoles which avoids solvents which are difficult to handle and dry, and at the same time avoids sticky, problematic azole hydrochloride precipitates.

There has now been a process for the preparation of N, N'-carbonyldiazoles of the formula

(I) found

in the X ¹ , X ² and X ³ each independently represent CR ¹ or nitrogen, where R ^{1 is} hydrogen or Ci- -alkyl and

R ^{2 represents} hydrogen,

or

X ¹ and X ^{3 are} CR ¹ , the R ¹ on X ^{1 being} hydrogen or C _j -C ₆ alkyl and the R ¹ on X ³ together with R ^{2 being} a - CH = CH-CH = CH- Forms bridge, and

X ^{2 represents} CR ¹ or nitrogen, where R ^{1 is} hydrogen or C ₆ -C ₆ -alkyl,

by reacting azoles of the formula (II),

in which the symbols used have the meaning given for formula (I),

with phosgene in a solvent, which is characterized in that the azole of the formula (II) is metered in with phosgene into an aromatic solvent dehydrated by distillation in such a way that, in the time in which 1 mol of azole of the formula is metered in, 0 17 to 0.34 mol of phosgene are metered in.

In the process according to the invention, the azole hydrochloride (for example imidazole hydrochloride) which precipitates in the reaction always and surprisingly always remains as a disperse, crystalline precipitate that does not form caking and sticking to the stirrer or vessel wall. Due to the disperse nature of the precipitation, the stirring resistance is significantly lower than when the method is not according to the invention. It is therefore possible, according to the invention, to use significantly higher reactant concentrations than previously, which results in a significantly improved space yield compared to the prior art. According to EP-A2 692 476, a reactant concentration of 12% by weight is used and a space yield of about 70 g / l is achieved while working with reactant concentrations of, for example, 28 to 33% by weight using the process according to the invention Can achieve space yields of, for example, 120 to 175 g / 1. Can too

Damage to the reactor and its internals due to hard azole hydrochloride conglomerates can be excluded.

In the process according to the invention, the azole hydrochloride is also crystalline towards the end of the metering in of azoles of the formula (II) and phosgene

Precipitation before. It can be easily and completely flushed out of the reactor into a filtering device with the reaction mixture. The filtration times are short due to the crystallinity of the precipitate.

Preferably, only one azole of the formula (II) is used in the process according to the invention, and an N, N'-carbonyldiazole of the formula (I) is obtained in which the two azole rings are identical.

It is further preferred that in formulas (I) and (II) one or two of the molecular parts X ¹ , X ² and X ^{3 are} nitrogen. It is also preferred that X ¹ for

CH, X ^{2 are} nitrogen and X ^{3 are} CR ', where R ¹ and R ² together form a -CH = CH-CH = CH bridge.

It is particularly preferred to use imidazole, benzimidazole, pyrazole or 1,2,4-triazole as azole of the formula (II) in the process according to the invention. Imidazole is very particularly preferred here. Phosgene can be used in the usual technical quality. It is advantageous to use 0.2 to 0.3 mol, in particular 0.22 to 0.27 mol, of phosgene per mole of azole of the formula (II). It is particularly preferred to use 0.25 mol of phosgene per mole of azole of the formula (II).

It is an essential feature of the present invention that the azole of formula (II) and phosgene are fed to the reaction mixture in a kind of simultaneous metering.

As aromatic solvents there are e.g. Benzene, toluene, xylenes, monochlorobenzene, dichlorobenzenes, trichlorobenzenes and mixtures of these solvents are suitable. Before the reaction of azoles of the formula (II) with phosgene, they are dewatered in a simple manner by distillation.

Distillation to drain the solvents can e.g. so happen that the respective solvent is heated to boiling temperature before use at normal or reduced pressure until no more discharge of water is observed. In general, between 0.1 and 5, preferably between 0.5 and 2% by weight of the solvent is distilled off.

The azole used can be in the form of a solution or suspension at a temperature of e.g. 20 to 120 ° C, preferably 60 to 100 ° C, can be metered into the abovementioned solvents or as a melt. This type of dosing makes it easier to control the dosing speed.

The method according to the invention can e.g. be carried out at temperatures of 50 to 120 ° C. Preferably one works at 70 to 100 ° C.

It is advantageous before the simultaneous metering of the azole and the phosgene up to 10 wt .-%, preferably 0.1 to 1 wt .-% of the total amount of azole in Submit the reaction vessel and then start the simultaneous dosing of azole and phosgene. Thus, even at the beginning of the reaction, the unfavorable state that phosgene is present in a clear excess (molar ratio of phosgee azole = 0.3 or higher) cannot occur. Such high molar ratios favor the decomposition of the azole with a darkening of the reaction mixture.

In general, it is advantageous to add the reaction mixture for some time after e.g. Stir for 30 minutes to 5 hours at elevated temperature.

The reaction mixture can e.g. Work up so that the azole hydrochloride precipitate formed is separated at 50 to 120 ° C, preferably at 70 to 100 ° C, by filtration. The filtration works well due to the consistency of the precipitation.

It was further found that the N, N'-carbonyldiazole can be isolated from the mother liquor obtained in the hydrochloride separation if the mother liquor is cooled to +40 to -70 ° C, preferably to +25 to -20 ° C, and the product which crystallizes out is filtered off. The product is obtained in a well crystallized form in purities of over 95%.

In contrast, the mother liquor of the hydrochloride separation is completely concentrated according to the prior art. Then any impurities that may be present in the mother liquor remain in the product. The N, N'-carbonyldiazole obtained according to the prior art is also partially amorphous, tends to

Atomize and is more sensitive to moisture.

Half of the azole used is obtained as azole hydrochloride, which according to the prior art appears to have to be disposed of or otherwise used. It has also been found that an azole which has been wholly or partly obtained from azole hydrochloride, in particular from, can be used in the process according to the invention Azole hydrochloride, which is obtained as a by-product in the synthesis of N, N'-carbonyldiazole.

The recovery of azoles from azole hydrochlorides can e.g. be carried out in such a way that azole hydrochlorides, in particular in the synthesis of N, N'-

Azole hydrochlorides formed in carbonyldiazoles, in a solvent mixture comprising, on the one hand, an aromatic solvent such as benzene, toluene, a xylene, monochlorobenzene, a dichlorobenzene, a trichlorobenzene or mixtures thereof, preferably in the solvent in which the synthesis of N, N'-carbonyldiazole was carried out, and on the other hand a solvent of the formula

R ⁴ OH (III),

in the

R ^{4 represents} hydrogen or C j -C ₄ alkyl,

with a compound of the formula

M (OR ⁴ ) _n (IV),

in the

n corresponds to the valence of M,

M represents an alkali or alkaline earth metal and

R ^{4 has} the meaning given for formula (III),

implements. In the formulas (III) and (IV), R ⁴ preferably represents hydrogen or methyl, in formula (IV) M preferably represents lithium, sodium or potassium.

It is advantageous after the reaction of the azole hydrochloride with the compound of the formula (IV) to distill off all of the compound of the formula (III), including the compound of the formula (III) formed in the reaction of azole hydrochloride and the compound of the formula (IV), filter off the salt MCl _{n formed} at normal or elevated temperature and use the azole obtained either directly in the aromatic solvent or after separating off the aromatic solvent for the inventive N, N'-carbonyldiazole synthesis.

This procedure works particularly well if LiOH, NaOH or KOH is used as the compound of the formula (IV) in a solvent mixture of water (that is a compound of the formula (III) with R ⁴ = hydrogen) and chlorobenzene, Tokyo !. Xylul or 2-methyltetrahydrofuran is used and the water is removed by azeotropic distillation, for example by separating it on a water separator, or if, as a compound of the formula (IV), sodium methylate is used in a solvent mixture of methanol on the one hand and chlorobenzene or xylene on the other and the methanol is separated off by distillation, for example by distilling it off from the mixture through an effective column.

In summary, it is surprising that by controlling the starting material metering according to the invention it is possible to produce the by-product (azole hydrochloride) in a non-sticky consistency and thus to improve the stirring properties of the reaction solution, to make it possible to achieve higher space yields and to easily remove the azole hydrochloride from the Ensure the reaction vessel. Exclude damage from hardened azole hydrochloride and keep the filtration times short. Further advantages of special embodiments of the present invention are the provision of a workup in which the N, N'-carbonyldiazoles are obtained in crystalline, readily filterable form and in which the

By-product formed azole hydrochloride is recovered and again in the syn- thesis of N, N'-carbonyldiazole can be used. The latter means around a doubling of the yield of N, N'-carbonyldiazole, based on the azole used.

Examples

example 1

1,000 g of chlorobenzene, dried by distillation, were placed in a flask and heated to 75.degree. A solution of 408.6 g of imidazole in 410 g of dried chlorobenzene was placed in a dropping funnel heated to 75 ° C. The 818.6 g imidazole solution were then simultaneously introduced at 75 ° C. in a period of 1.5 hours at a rate of 8.6 g / min and 158.2 g of phosgene at a rate of 100 g / h. After the addition was complete, stirring was continued at 80 ° C. for 1 hour while passing through a vigorous stream of nitrogen. The imidazole hydrochloride precipitate was filtered off and washed with 200 g of chlorobenzene at 80 ° C. The combined filtrates were cooled to 20 ° C. The precipitated carbonyldiimidazole precipitate was filtered off, washed with 200 g of dried chlorobenzene and opened at 60 ° C. at 50 mbar.

213.7 g of colorless crystals (97.7% carbonyldiimidazole, 85.8% of theory) were obtained.

Example 2

500 g of chlorobenzene dried by distillation were placed in a flask and heated to 80.degree. A solution of 500.0 g of imidazole in 500.0 g of dry chlorobenzene was placed in a dropping funnel heated to 75 ° C. 100 g of the solution were metered into the initially introduced chlorobenzene and then the remaining 900 g of imidazole solution at a rate of 10 g / min and 200.0 g of phosgene at a rate of 2 simultaneously at 85 ° C. in 1.5 hours. 2 g / min initiated. After the addition had ended, stirring was continued at 80 ° C. for 1 hour while passing through a vigorous nitrogen stream. The imidazole hydrochloride precipitate was filtered off and washed with 200 g of chlorobenzene at 80 ° C. The combined filtrates were cooled to 20 ° C. The precipitated carbonyldiimidazole precipitate was filtered off with 200 g of dried Washed chlorobenzene and dried at 60 ° C at 50 mbar. 265.0 g of colorless crystals (98.0% carbonyldiimidazole, 89.0% of theory) were obtained.

Example 3

369.7 g of imidazole hydrochloride (obtained in Example 1) were placed in a distillation apparatus in 1200 g of chlorobenzene. 486.0 g of a 30% strength by weight methanolic sodium methylate solution were added dropwise. After the addition had ended, the methanol was distilled off. The distillation bottoms were filtered off at 100 ° C. from the sodium chloride formed and the filtrate was cooled to 0 ° C. The imidazole which precipitated was filtered off. 177.0 g of imidazole were obtained.

Example 4

500.0 g of chlorobenzene dried by distillation were placed in a flask and heated to 75.degree. A solution of 323.0 g of fresh imidazole and the 177.0 g of imidazole (obtained in Example 3) in 500.0 g of dried chlorobenzene were placed in a dropping funnel heated to 75 ° C. 1,000 g of imidazole solution were simultaneously introduced at a rate of 11 g / min and 200.0 g of phosgene at a rate of 2.2 g / min in 1.5 hours. The temperature was kept at 76 to 79 ° C. After the addition was complete, stirring was continued at 80 ° C. for 1 hour while passing through a vigorous stream of nitrogen. The imidazole hydrochloride precipitate was filtered off and washed with 200 g of chlorobenzene at 80 ° C. The combined filtrates were cooled to 20 ° C. The precipitated carbonyldiimidazole precipitate was filtered off, washed with 200.0 g of dried chlorobenzene and dried at 60 ° C. and 50 mbar. 255.0 g of colorless crystals (97.5% carbonyldiimidazole, 83.3% of theory) were obtained.

Claims

claims

1. Process for the preparation of N, N'-carbonyldiazole of the formula (I)

in the

X ¹ , X ² and X ³ each independently represent CR ¹ or nitrogen, where R ^{1 is} hydrogen or C _j -C ₆ alkyl and

R ^{2 represents} hydrogen,

or

X ¹ and X ^{3 are} CR ¹ , the R ¹ on X ^{1 being} hydrogen or C Cg-alkyl and the R ¹ on X ³ together with R ² forming a -CH = CH-CH = CH bridge, and

X ^{2 represents} CR ¹ or nitrogen, where R ^{1 is} hydrogen or C _r C ₆ alkyl,

by reacting azoles of the formula (II),

in which the symbols used have the meaning given for formula (I),

with phosgene in a solvent, characterized in that the azole of the formula (II) is metered in with phosgene into an aromatic solvent dehydrated by distillation in such a way that during the time in which 1 mol of azole of the formula (II) is metered in, 0 , 17 to 0.34 mol of phosgene are metered in.

2. The method according to claim 1, characterized in that in the formulas (I) and (II) one or two of the molecular parts X ¹ , X ² and X ^{3 are} nitrogen.

3. Process according to claims 1 and 2, characterized in that one per

Mol of azole of the formula (II) uses 0.2 to 0.3 mol of phosgene.

4. Process according to Claims 1 to 3, characterized in that benzene, toluene, xylenes, monochlorobenzene, dichlorobenzenes, trichlorobenzenes or mixtures of these solvents are used as aromatic solvents and these are heated to boiling temperature before use at normal or reduced pressure until no more discharge of water is observed.

5. Process according to claims 1 to 4, characterized in that it at

Performs temperatures in the range of 50 to 120 ° C. Process according to Claims 1 to 5, characterized in that up to 10% by weight of the total amount of the azole is placed in the reaction vessel before the simultaneous metering in of the azole and the phosgene is started.

Process according to Claims 1 to 6, characterized in that the reaction mixture is worked up in such a way that the azole hydrochloride precipitate formed is separated off at 50 to 120 ° C by filtration and isolated from the mother liquor N, N'-carbonyldiazole by adding the mother liquor Cools from +40 to -70 ° C and the product which crystallizes out is filtered off.

Process according to Claims 1 to 7, characterized in that an azole is used which has been wholly or partly obtained from azole hydrochloride.

Process according to Claims 1 to 8, characterized in that azole is recovered from the azole hydrochloride by reacting the azole hydrochloride in a solvent mixture of an aromatic solvent and a solvent of the formula

R OH (III),

in the

R ^{4 represents} hydrogen or C _λ -C ₄ - alkyl 1,

with a compound of the formula

M (OR) _n (IV),

in the n corresponds to the valence of M,

M represents an alkali or alkaline earth metal and

R ^{4 has} the meaning given for formula (III),

implements.

10. The method according to claim 9, characterized in that as compound of formula (IV) LiOH, NaOH or KOH in one

Solvent mixture of water and chlorobenzene, toluene, xylene or 2-methyltetrahydrofuran is used, the water is removed by azeotropic distillation or, as a compound of the formula (IV), sodium methylate is used in a solvent mixture of methanol on the one hand and chlorobenzene or xylene on the other hand and the methanol is separated off by distillation.