EP1549610A2

EP1549610A2 - Method for catalyst-free production of cyanophenols from methoxybenzonitriles

Info

Publication number: EP1549610A2
Application number: EP03797265A
Authority: EP
Inventors: Jürgen SANS; Hans-Georg Erben; Franz Thalhammer; Mario Gomez Andreu
Original assignee: Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2002-09-11
Filing date: 2003-09-04
Publication date: 2005-07-06
Also published as: WO2004026812A3; WO2004026812A2; DE10242080A1; US20060173207A1; JP2005538179A

Abstract

According to the inventive method for catalyst-free production of cyanophenols from methoxybenzonitriles, substituted methoxybenzonitriles of general formula (I) are reacted with an alkali alcoholate at temperatures of 80 - 230 °C. The inventive method is based on simple, low-cost and easily accessible raw materials and can be carried out in technically simple conditions, enabling cyanophenols to be produced with high and partially quantitative yields with guaranteed low waste levels. Sodium methanolate is used as a preferred alkali alcoholate at preferred temperatures of 140 - 180 °C. The methoxybenzonitrile component can optionally be produced by ammonoxidation of a methoxytoluol of ammonia and (air-)oxygen and be directly further reacted.

Description

Process for the catalyst-free production of cyanophenols from methoxybenzonitriles

description

The present invention relates to a process for the catalyst-free preparation of cyanophenols.

A common, technically established and in the literature [K. Weissermel, H.-J. Arpe, Industrial Organic Chemistry, 3rd revised and expanded edition, VCH Weinheim, 1988, p.376] The process for the preparation of phenols described in detail is the known conversion of an isopropylaromatic with oxygen and the subsequent conversion to phenol and acetone (Hock's phenol synthesis). Disadvantage of this

The process is the equimolar amount of acetone and the high consumption of propene for the production of the isopropylaromatic. In addition, any substituted cyanophenols cannot be produced using this method.

With the already classic method [K. Weissermel, H.-J. Arpe, Industrial Organic Chemistry, 3rd revised and expanded edition, VCH Weinheim, 1988, p.370] for the production of phenols from benzenesulfonic acids, large amounts of salts (Na2S03, Na2S04) are obtained as a by-product, so that the process is environmentally friendly western world can no longer be used.

The production of phenols from chloroaromatics using NaOH is also known from the literature and is technically realized [K. Weissermel, H.-J. Arpe, Industrial Organic Chemistry, 3rd revised and expanded edition, VCH Weinheim, 1988, p.372]. T. drastic reaction conditions and especially the temperatures above 360 ° C are considered disadvantageous. Transfer to substituted phenols, such as. B. Cyanophenols is not possible due to the required reaction conditions.

The preparation of cyanophenols by the construction of the cyan unit is also well known and described. Thus, the cyano function can be built up from the corresponding aromatic aldehydes with hydroxylamine and auxiliary reagents or from aldehydes with ammonia and auxiliary reagents, for which a wide variety of processes are used. [A. K. Chakraborti et al., Indian Journal of Chemistry, Section B: (2001), 40B (10), 1000-1006 .; B. Das et al., Synlett (2000), (11), 1599-1600; G. Lai et al., Synlett (2001), (2), 230-231 .; A.R. Bajpai, et al., Synthetic Communications (2000), 30 (15), 2785-2791; A. S. Paraskar et al., J. Chem. Res., Synop. (2000), (1), 30-31; A.K. Chakraborti, Tetrahedron (1999), 55 (46), 13265-13268; H.M. Kumar et al., Synthesis (1999), (4), 586-587; G. Sabitha et al., Synth. Commun. (1998), 28 (24), 4577-4580; E. Wang et al., Tetrahedron Lett. (1998), 39 (23), 4047-4050; H. M. Meshram, Synthesis (1992), (10), 943-4; D. Konwar, et al., Tetrahedron Lett. (1990), 31 (7), 1063-4; P. Capdevielle et al., Synthesis (1989), (6), 451-2; G. Jin et al., (1985), 21 (3), 506-8; J.C. Vallejos et al., FR 2 444 028; H. Schlecht, DE 20 14 984].

Even if these processes sometimes result in good to very good yields, the use of the expensive aromatic aldehydes is in any case to be regarded as disadvantageous. Furthermore, the use of the easily decomposing hydroxylamine and / or the use of ammonia and the expensive and mostly environmentally hazardous auxiliary reagents is necessary. The alternative offered by microwave radiation is technically demanding and also too expensive.

It is also known to build a nitrile function from the corresponding acids and ammonia using dehydrating agents and at high temperatures, although the raw materials and the extreme reaction conditions prevent wide use. The ammoxidation of methylphenols to the corresponding cyanophenols is also known from the literature [MV Landau et al., Applied Catalysis, A: General (2001), 208 (1,2), 21-34; A. Martin et al., J. Prakt. Chem. (1990), 332 (4), 551-6; H. Bruins Slot, DE 2037 945], but this is only possible in very modest yields. In addition to the low yield, the disadvantage of these processes is the high outlay for industrial synthesis. The same applies to the structure of the nitrile function from a benzoic acid and ammonia or from an ester and ammonia, according to the following references [R. Ueno et al., EP 74 116; M. Araki et al., JP 53040737; R. Perron, FR 2 332 261; G. Bakassian, M. Lefort, DE 22 05 360; H. Eilingsfeld, E. Schaffner, DE 20 20 866; T. Ichii et al., JP 43029944].

References to ether cleavage for the formation of phenols can also be found in the literature [P. R. Brooks et al., Journal of Organic Chemistry (1999), 64 (26), 9719-9721]. The stoichiometric use of the expensive raw materials boron trichloride and the use of large amounts of n-butylammonium iodide are particularly disadvantageous in this process.

Systems that have been specially developed for the cleavage of allyl ethers are also described in the present context. Systems from CeCI3 and Nal can be used for this [RM Thomas et al., Tetrahedron Letters (1999), 40 (40), 7293-7294] or NaBH4 [RM Thomas et al., Tetrahedron Lett. (1997), 38 (26), 4721-4724], or else electrochemical processes [D. Franco et al., Tetrahedron Lett. (1999), 40 (31), 5685-5688; A. Yasuhara et al., J. Org. Chem. (1999), 64 (11), 4211-4213; K. Fujimoto et al., Tetrahedron (1996), 52 (11), 3889-96; S. Olivero et al., J. Chem. Soc, Chem. Commun. (1995), (24), 2497-8]. The latter process variant is expensive, however, and it always requires the use of heavy metals. In addition, this process variant is restricted exclusively to the allyl ethers, which are complex to synthesize. The production of nitrophenols from nitroaromatics by substituting hydrogen with hydroperoxide anions and in the presence of strong bases is a very interesting process, but unfortunately limited to nitroaromatics; in addition, the use of liquid ammonia and easily decomposable and therefore dangerous hydroperoxides is necessary

[M. Makosza et al., J. Org. Chem. 1998, 63, 4199-4208]. To produce cyanophenols, the nitro group has to be converted into a cyano group in a complex process.

T. Senba and K. Sakano (JP 09023893) and H. Semba et al. describe the enzymatic synthesis of phenols [Appl. Microbiol. Biotechnol. 1996, 46, 432-437]. Due to the low space-time yields and the long reaction times, this process cannot be used economically.

The synthesis of phenols from anilines by diazotization and decomposition of the diazonium compound in the presence of metals, especially Cu salts, has also been known for a long time. Even if newer attempts have been made to optimize the process [B.C. Gilbert et al., EP 596 684], the route always leads via a difficult to handle diazonium compound.

According to S. Prouilhac-Cros, et al. the production of phenols from arylsilanes with H202 and stoichiometric amounts of fluoride would lead to phenols in good yields [Bull. Soc. Chim. 1995, 132, 513-16]. However, the arylsilane required is not sufficiently available in technical quantities.

The synthesis of phenols from aryl methyl ether with ethanethiolates is limited to laboratory applications [JA Dodge et al., J. Org. Chem. 1995, 60, 739-41]. The reaction is unsuitable for industrial syntheses because toxic and malodorous sulfur compounds are produced. The cleavage of aryl methyl ethers using the FeO / glacial acetic acid / oxygen system is also described [AF Duprat et al., J. Mol. Catal. 1992, 77]. This process is limited to particularly activated aromatics and gives the desired products only in low to very low yields. Only slightly better yields in the cleavage of aryl methyl ethers are obtained with AICI3 / NaCI [G. Adamska, et al., Biul. Wojsk. Akad. Tech. 1980, 29, 93-99]. The resulting large amounts of inorganic waste do not allow the process to be used industrially. The AICI3 / Ni system described in the literature for the cleavage of these ethers also offers no advantages, since temperatures above 240 ° C. and long reaction times are required [H. Kashiwagi, S. Enomoto, Yakugaku Zasshi 1980, 100, 668-71].

A very complex process for cleaving aryl methyl ethers and for producing hydroxybenzonitrile is the re-methylation (e.g. FR 1 565812), according to which the reaction of methoxybenzonitrile with the Na salt of cresol to the Na salt of hydroxybenzonitrile and methoxycresol at temperatures above 200 ° C he follows. This process delivers large amounts of waste and is very complex to carry out. Although the aryl methyl ethers are in principle very suitable raw materials, the cleavage of the ether is very difficult; alternative fission methods are not available.

All of the processes mentioned lead to the desired products and they have already been used successfully for a large number of different applications. However, all of these processes for the production of phenols and especially cyanophenol have the disadvantage that they are very complex to carry out, that expensive raw materials have to be used, that large amounts of waste are produced or that the yield is very low. The object of the present invention was therefore to develop a process for the catalyst-free production of cyanophenols which allows the environmentally friendly and low-waste production of the desired product with cheap raw materials in high yields. In particular, the use of heavy metals, as is customary, for example, when using metals as a catalyst, should be avoided.

This object was achieved with a corresponding process in which a substituted methoxybenzonitrile of the general formula (I)

wherein R1, R2, R3 and R4 independently of one another are hydrogen, a C1-10

Alkyl, C2-8-alkoxy, aryl, a phenoxy or another nitrile group mean, is reacted with an alkali metal alcoholate at temperatures between 80 and 230 C.

Surprisingly, it was found that not only can catalysts for carrying out the reaction be completely dispensed with as desired, and that the cyanophenols are obtained in very good yields and purities, but also that a process which is relatively simple to carry out is available and which has no problems on an industrial scale Scope can be carried out without the by-products. The selection of aromatic raw materials is not only restricted to simple methoxybenzonitriles, but rather also includes substituted methoxybenzonitriles, di-, tri-, tetra- or pentamethoxybenzonitriles being particularly suitable.

Methanolates, including, in particular, sodium methoxide, are to be regarded as the preferred alkali alcoholate component.

The method according to the invention can be carried out within a relatively wide temperature range. But have

Reaction temperatures proven to be particularly suitable, which are between 120 and 200 ° C and very particularly preferably between 140 and 180 ° C.

Typically, the reaction works best when the molar ratio of the methoxybenzonitrile component to the alkali alcoholate component is 1: 0.5 to 1.5, and particularly preferably 1: 1.0 to 1.1.

The present process is usually successful even without the presence of a solvent. However, the present invention also provides for the use of a suitable solvent, in which case both polar and non-polar solvents can be used. C1-6 alcohols, such as. B. methanol, and / or a solvent of the series tetrahydrofuran, benzene, toluene, xylene and methyl tert-butyl ether. In particular, the use of simple alcohols, such as. B. methanol.

The preferred reaction is usually carried out by placing the alcoholate component in an alcohol (for example sodium methoxide in methanol), then adding the methoxybenzonitrile component, which is preferably carried out with stirring; this should preferably be done in an autoclave, with the required one Reaction temperature is heated and this is held until the desired conversion is reached.

The order in which the starting materials are added is not restricted to this preferred sequence. Rather, the reaction can also be carried out by adding the individual components in a different order. The addition of the individual components, in particular the addition of the methoxybenzonitrile component to the alcoholate, can also be staggered over the course of a longer period of time or else continuously.

The required aromatic raw materials, the methoxybenzonitriles, can also be produced according to the prior art by ammoxidation in a simple, environmentally friendly and almost waste-free manner from the corresponding methoxytoluenes and in the presence of ammonia and (atmospheric) oxygen, which the present invention is particularly suitable for Process variant provides.

It is also provided that the methoxybenzonitrile component is not isolated, but that it is implemented directly in the sense of the invention.

The new process according to the invention thus allows the catalyst-free production of cyanophenols from methoxybenzoniriles in high yields and thus also guarantees a small amount of waste.

The present process also describes for the first time a process for the production of cyanophenols, which starts from simple, inexpensive and easily accessible raw materials and runs under conditions that are technically easy to implement. Examples

Example 1 26.6 g of anhydrous 4-methoxybenzonitrile were added to 39.6 g of 30% methanolic anhydrous sodium methoxide solution and heated to 175 ° C. in an autoclave at a starting pressure of 5 bar nitrogen with stirring. After 8 hours, the mixture was cooled, then 100 ml of water were added and only a small amount of solid (<0.1 g) was filtered off. In the cold, as much 32% hydrochloric acid was then added to the filtrate until a pH of 2 was reached. After 60 minutes, the precipitate formed was filtered off. After drying, 20 g of the product 4-cyanophenol were obtained in this way. (84.1% of theory).

Example 2

26.6 g of anhydrous 4-methoxybenzonitrile were added to 54 g of 30% methanolic anhydrous sodium methoxide solution and heated to 155 ° C. in an autoclave at 5 bar nitrogen as the starting pressure with stirring. After 12 hours the mixture was cooled, then 90 ml of methanol and 80 ml of water were added and only a small amount of solid (<0.1 g) was filtered off. In the cold, as much 32% hydrochloric acid was then added to the filtrate until a pH of 2 was reached. After 60 minutes, the precipitate formed was filtered off. After drying, 20.2 g of the product 4-cyanophenol (84.9% of theory) were obtained in this way.

Example 3

18.8 g of anhydrous 4-methoxybenzonitrile were added to 49 g of 25% methanolic anhydrous sodium methoxide solution and heated to 140 ° C. in an autoclave with a starting pressure of 5 bar nitrogen as the starting pressure with stirring. After 8 hours the mixture was cooled and then 162 ml of water was added. In the cold, a 32% added hydrochloric acid until a pH of 2 was reached. After 60 minutes, the precipitate formed was filtered off. After drying, 15 g of the product 4-cyanophenol (89.3% of theory) were obtained.

Example 4

26.6 g of anhydrous 4-methoxybenzonitrile were added to 97.2 g of 21% ethanolic anhydrous sodium ethanolate solution and heated to 160 ° C. in an autoclave with stirring. After 8 hours it was cooled and then 162 ml of water was added. In the cold, as much 32% hydrochloric acid was then added to the filtrate until a pH of 2 was reached. After filtering off the precipitate formed and after drying, 4.8 g of the product 4-cyanophenol (19.3% of theory) were obtained.

Example 5

18.8 g of anhydrous 2-methoxybenzonitrile were added to 49 g of 25% methanolic anhydrous sodium methoxide solution and heated to 140 ° C. with stirring at an initial pressure of 5 bar nitrogen in an autoclave. After 8 hours it was cooled and then 162 ml of water was added. A sufficient amount of 32% hydrochloric acid was then added in the cold until a pH of 2 was reached. After filtering off the precipitate formed and after drying, 16.8 g of the product 2-cyanophenol (100%) were obtained.

Claims

Expectations

1. A process for the catalyst-free preparation of cyanophenols from methoxybenzonitriles, characterized in that a substituted methoxybenzonitrile of the general formula (I)

wherein

R1, R2, R3 and R4 independently of one another denote hydrogen, a C1-10-alkyl, C2-8-alkoxy, aryl, a phenoxy or another nitrile group, with an alkali metal alcoholate at temperatures between 80 and

230 ° C is implemented.

2. The method according to claim 1, characterized in that di-, tri-, tetra- or pentamethoxybenzonitriles are used as the methoxybenzonitrile component.

3. The method according to any one of claims 1 or 2, characterized in that a methanolate, particularly preferably the sodium methoxide, is used as the alkali alcoholate.

4. The method according to any one of claims 1 to 3, characterized in that it is carried out at temperatures between 120 and 200 ° C and particularly preferably between 140 and 180 ° C.

5. The method according to any one of claims 1 to 4, characterized in that the molar ratio of the methoxybenzonitrile component to the alkali alcoholate component is 1: 0.5 to 1.5, and particularly preferably 1: 1, 0 to 1.1.

6. The method according to any one of claims 1 to 5, characterized in that it is in the presence of a polar and / or non-polar solvent, particularly preferably in the presence of a C1 -6 alcohol, such as. As methanol, and / or a solvent of the series tetrahydrofuran, benzene, toluene, xylene and methyl tert-butyl ether is carried out.

7. The method according to any one of claims 1 to 6, characterized in that the alcoholate component is placed in an alcohol, then the methoxybenzonitrile component is added and preferably heated with stirring, which is particularly preferably done in an autoclave.

8. The method according to any one of claims 1 to 7, characterized in that the methoxybenzonitrile component was produced by ammonoxidation of a methoxytoluene and in the presence of ammonia and (atmospheric) oxygen.

9. The method according to claim 8, characterized in that the methoxybenzonitrile component is reacted directly without isolation after the ammoxidation.