CH637134A5 - PROCESS FOR THE PREPARATION OF A CHROMOGENEIC COMPOUND. - Google Patents

Description

The present invention relates to a process for preparing a chromogenic compound of pyridine, as well as a material intended for recording and in which the system of bodies intended to form at least one color by their reaction comprises a chromogenic compound of pyridine prepared according to the invention.

Certain chromogenic pyridine compounds, corresponding to the 45 formulas IA and / or IB of Table A (where R1, R2, R3 and R4, identical or different, are each a hydrogen atom, an alkyl group having 1 to 4 atoms carbon or a phenyl group, and R5 is a hydrogen atom or an alkyl or alkoxy group having 1 to 4 carbon atoms) have been described, for example, in United States patents Nos. 3775424 and 3853869 and in Japanese patent application No. 48/53690. Such compounds are colorless materials capable of forming a color when brought into contact with a suitable acidic substance. They can therefore be used in pressure sensitive material to give recordings or copies, and in systems which can form traces and marks on multiple copy sheets. The aforementioned prior art also describes methods for preparing chromogenic pyridine compounds corresponding to formulas IA and / or IB in Table A. These methods generally start from quinoleic acid and com-60 take three separate steps. In such a process, the quinoleic acid is first transformed, in a first step, into the corresponding anhydride (see formulas Qi and Q2 in Table A).

Then, in a second step, the quinole anhydride (Q2) is reacted with an indole of formula II to obtain a mixture 65 of isomeric ketonic acids corresponding to formulas IIIA and / or IIIB of table B.

Finally, in a third step, the desired chromogenic compound of pyridine is obtained, corresponding to the formulas IA and / or IB in

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condensing the ketonic acids of formulas IIIA and / or IIIB, with an aromatic amine of formula IV and making the resulting reaction mixture alkaline (see formulas in Table C). In formulas II, IIIA, HIB and IV, the symbols R ', R2, R3, R4 and R5 correspond to the definition indicated with regard to formula IA or IB.

Up to now, the ketonic acids used for the reaction with the aromatic amine in the last stage of the process have always been removed from the previous stage, that is to say from the second stage of the process. In each of the cases described in the aforementioned prior art, the ketonic acids were collected by filtration, they were thoroughly washed, and even they were made to recrystallize in order to obtain a substance in the essentially pure or uncontaminated state. It was only then that the ketonic acids were condensed with an aromatic amine.

The overall yield can range, for this process, up to a maximum value of 48%, starting from quinoleic acid. However, according to the aforementioned prior art, the yields of the second and of the third stage, individually and separately, are only around 48% and 58%, respectively, which gives an overall yield of 28% from quinole anhydride. When you take into account the yield of the first stage, this yield of 28% will become even lower. The overall yields of pyrogenic chromogenic compounds corresponding to formulas IA and / or IB are thus very low when such compounds are prepared by the above process.

It has just been found that one can obtain from quinoleic anhydride (and quinoleic acid) a much better overall yield, for obtaining the chromogenic compound of pyridine corresponding to formulas IA and / or IB of Table A, if the above-mentioned process of the prior art is implemented without removing the ketonic acids of formulas IIIA and / or IIIB from the reaction mixture of the second step and, preferably also, without removing the anhydride quinoleic reaction mixture from the first step. The resulting process is eminently suitable for being carried out in a single container, and also continuously. This gives a more convenient procedure and a reduced reaction time, and contrasts with the process of the prior art according to which, after each step, the intermediates are effectively removed from the reaction mixtures of the first and second steps, and they are not washed and, in some cases, only recrystallizes it afterwards.

Therefore, the present invention provides a process for preparing a compound corresponding to the formulas IA and / or IB, according to the definition above. This process is characterized in that the quinole anhydride is reacted with an indole of formula II, according to the definition above, at a temperature between 65 and 75 ° C, to obtain a mixture of ketonic acids isomers of Forms IIIA and IIIB, as defined above; then they are reacted with an aromatic amine of formula IV, as defined above, and the pH of the resulting reaction mixture is adjusted to at least 8.

It is better to carry out the reaction between the quinole anhydride and the indole of formula II at a temperature of approximately 65 and 75 ° C. Below 65; C approximately, there is a mixture in two phases, whereas above this temperature a solution is obtained within which the reaction takes place quickly. Above 75 ° C, there is a risk of obtaining an unattractive amount of by-products.

In general, the indole of formula II is present in excess, and the reaction is carried out with quinoleic anhydride for approximately 3 hours.

It is better to carry out the reaction between the non-isolated ketonic acids corresponding to formulas IIIA and / or IIIB and the aromatic amine of formula IV at a temperature of approximately 45 to 55 ° C., for example at 50 C. Below 45 ° C, the reaction rate is too slow and, above 55 ° C, ketonic acids can start to decompose to form undesirable by-products.

The reaction is advantageously carried out with non-isolated ketonic acids corresponding to formulas IIIA and / or IIIB in the presence of acetic anhydride and for a period of approximately 4 h.

Adjustment of the pH of the resulting reaction mixture to at least 8, that is to say rather alkaline, is preferably carried out with sodium hydroxide which hydrolyzes the acetic anhydride possibly present and allows the formation of the nucleus. lactone of the chromogenic compound of pyridine corresponding to one of the formulas IA and / or IB. If desired, the reaction mixture can first be diluted with water.

Adjusting the pH to at least 8 precipitates the desired compound corresponding to formulas IA and / or IB, which can then be isolated by filtration of the reaction mixture to remove, for example, sodium acetate, and by washing for remove other impurities. For example, it is possible to apply a washing with one or more suitable hydrocarbons, in order to remove the aromatic amine of formula IV which may not have reacted, however, it is possible to use washing using the appropriate proportions. a mixture of water and an alkanol to remove unwanted strongly colored by-products. The alkanol which is used is preferably methanol, ethanol or isopropanol, and it can be used in proportions of 30 to 50% in water. However, any proportion can be used as long as it is capable of removing the colored by-products without dissolving excessive amounts of the pyridine corresponding to formulas IA and / or IB.

The process of the invention encompasses the possibility of carrying out a washing operation on ketonic acids, such as a washing by siphoning, using for example benzene or chlorobenzene. Such an operation is in fact advantageous since it removes any possible excess of the indole of formula II, which can then be collected, and also of bisindolylpyridine, useful chromogenic compound of formula V of table B (where R1 and R2 have the meaning defined in relation to formulas I) and which may have been obtained as a by-product. If the excess indole of formula II is not removed, this excess may, in the subsequent stage of the process, compete with the isomeric ketonic acids corresponding to formulas III for the reaction with the amine aromatic of formula IV. Thus, the inclusion in the process of a washing operation carried out on the ketonic acids corresponding to the formulas III makes it possible to further improve the overall yield, and also to carry out the convenient removal of the chromogenic by-product.

One of the starting materials for the process of the invention, quinoleic anhydride, can be prepared by a reaction between commercially available quinoleic acid and acetic anhydride, according to the first step of the process of the art prior. However, it is preferred not to remove the resulting quinoline anhydride from the reaction mixture before the subsequent reaction with an indole of formula II in Table B.

Quinoleic anhydride is conveniently prepared by operating at a temperature of about 120 to 130 ° C. The reaction does not proceed at a satisfactory rate below 120 ° C, while an upper limit of 130 ° C is appropriate, since the boiling point of acetic anhydride is reached at 140 ° C.

It is desirable to use an excess of acetic anhydride relative to quinoleic acid, and the time required to complete the reaction is usually between 10 and 20 min.

The process of the invention comprises the possibility of carrying out a washing operation on the resulting quinoleic anhydride, in particular a washing with siphoning of carbon tetrachloride,

in order to remove the acetic acid and the unaltered acetic anhydride which may be present. The removal of the latter compound may be advantageous since its presence in the next reaction step risks facilitating the production of a larger amount of the chromogenic bisindolinepyridine of formula V in Table B.

The chromogenic pyridines of formulas IA and / or IB which are preferably prepared by the process of the present invention are those in which R1, R2, R3 and R4 are each a methyl or ethyl radical and R5 is a methyl or methoxy radical or ethoxy. The most preferred compounds are those in the formula of which R2, R3 and R4 are each an ethyl radical, R1 is a methyl radical and Rs is a methoxy radical. The compounds corresponding to formulas IA and IB usually serve, in the form of a mixture of the isomers obtained, as components of forma-

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tion of a color in paper to obtain carbon-free copies and, in other materials, to obtain copies and recordings for files. Systems and assemblies of such components are well known in practice and are described, for example, in the aforementioned United States patents Nos. 3775424 and 3853869 and in United States patent No. 3627581. Compounds prepared by the process of the present invention can play the role of the colorless chromogenic compound in such systems.

Here is a nonlimiting example illustrating the present invention. Unless otherwise indicated, the percentages are by weight.

Example:

In a 100 ml round bottom flask, 5.01 g (0.03 mol) of 2,3-pyridinedicarboxylic acid (quinoleic acid) and 9 ml (0.06 mol) of acetic anhydride are placed. By heating at 120-130 ° C for 20 min, a clear solution is obtained. Upon cooling and as soon as crystallization begins, 60 ml of CC14 are added. The mixture of CC14, acetic anhydride and acetic acid is removed by siphoning. Three additional washings are carried out with 10 ml each of CC14.

To the solid present in the reaction flask, 6.88 g (0.0433 mol) of 1-ethyl-2-methylindole is added. The mixture is kept at 65-70 "C for 3 h. During this time, a mixture of a liquid and a solid is present which can be stirred. To the cooled reaction mixture, 50 is added. ml of benzene (or chlorobenzene) The benzene and the soluble constituents are removed by siphoning, and two additional washes are carried out with 15 ml each.

To the ketonic acids remaining in the reaction flask, 4.63 g (0.024 mol) of N, N-diethyl-m-phenetidine and 32 ml of acetic anhydride are added. After 4 hours at 55 ° C., the reaction suspension is poured into 250 ml of water containing 28 g of sodium hydroxide, the precipitated product is stirred for 1 hour at 50 ° C. This product is filtered, then washed several times with water, with 20 ml of water containing 30% methanol, and finally with 15 ml of petroleum ether (boiling between 60 ° and 110 ° C.) The overall yield of isomeric chromogenic compounds , 7- (1-ethyl-2-methylindol-3-yl) -7- (4-diethylamino-2-ethoxyphenyl) -15 5,7-dihydrofuro [3,4-b] -pyridine-5-one and 5- (1-ethyl-2-methylindol-3-yl) -5- (4-diethylamino-2-ethoxyphenyl) -5,7-dihydrofuro [3,4-b] -py-ridine-7-one, is 74% relative to the starting pyridine-2,3-dicarboxylic acid The ratio of isomers in the product obtained is about 20: 1, respectively, and it is determined experimentally that the overall ratio to from the pyridine-2,3-dicarboxylic acid anhydride is about 86%, and the yield of bisindolylpyridine produced and isolated as a by-product is 7.8%.

It goes without saying that numerous modifications can be made to the process described, without departing from the scope of the invention.

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2 sheets of drawings

Claims (10)

637,134 2 1. Process for preparing a compound corresponding to one of the formulas (IA) and (IB) or for preparing one of their mixtures: R R (IA) (IB) where R1, R2, R3 and R4, identical or different, are each a hydrogen atom, an alkyl radical having 1 to 4 carbon atoms or a phenyl radical, and Rs is a hydrogen atom or an alkyl or alkoxy radical having 1 to 4 carbon atoms, this process being characterized in that quinoline anhydride is reacted with an indole of formula (II): R JOD R ' where R1 and R2 have the meaning defined above, at a temperature between 65 and 75 C, to obtain a mixture of isomeric ketonic acids of formulas (IIIA) and (HIB): 0 (HIB) where R1 and R2 have the meaning defined above; then they are reacted with an aromatic amine of formula (IV): (IV) where R3, R4 and R5 have the meaning defined above, and the pH of the resulting reaction mixture is adjusted to at least 8. 2. Method according to claim 1, characterized in that the ketonic acids corresponding to the formulas (IIIA) or (IIIB) are reacted with the aromatic amine of formula (IV) at a temperature between 45 and 55 C. 5 3. Method according to claim 2, characterized in that the reaction is carried out in the presence of acetic anhydride. 4. Method according to one of claims 1 to 3, characterized in that the pH is adjusted with sodium hydroxide. 5. Method according to one of claims 1 to 4, characterized in that the ketonic acids corresponding to the formulas (IIIA) are washed and (IIIB) by siphoning with benzene or chlorobenzene before reacting them with the aromatic amine of formula (IV). 6. Application of the method according to claim 1 to a quinoleic anhydride obtained by reaction between quinoleic acid and 15 acetic anhydride. 7. Use according to claim 6, consisting in carrying out the subsequent reaction with the indole of formula (II) without removing the quinoleic anhydride from the reaction mixture obtained according to claim 6. 8. Use according to claim 6, consisting in carrying out the reaction between quinoleic acid and acetic anhydride to obtain quinoleic anhydride at a temperature between 120 and 130 C. 9. Application according to claims 6 to 8, consisting in washing the quinoleic anhydride by siphoning with carbon tetrachloride before reacting it with an indole of formula (II). 10. Application according to one of claims 6 to 9, carried out in a single reaction vessel. 11. Application according to claim 10, implemented continuously. 12. Application according to one of claims 6 to 10, according to which the symbols R1, R2 and R4 are each a methyl or ethyl radical, while the symbol R5 is a methyl, methoxy or ethoxy radical. (II) (IIIA)