GB2031934A

GB2031934A - Chromogenic pyridine compounds

Info

Publication number: GB2031934A
Application number: GB7942732A
Authority: GB
Original assignee: Appleton Papers Inc
Current assignee: Appvion Operations Inc
Priority date: 1977-09-29
Filing date: 1978-09-25
Publication date: 1980-04-30
Also published as: DE2842263C2; CH637134A5; CH649555A5; GB2006248B; CA1110244A; HK73384A; HK73884A; DE2842263A1; GB2031934B; JPS5452095A; GB2006248A; FR2408609B1; FR2408609A1

Abstract

The colour former compound 7-(1- ethyl-2-methyl-indol-3-yl)-7-(4- diethylamino-2-ethoxy-phenyl)-5,7- dihydrofuro {3,4-b}-pyridine-5-one and/or 5-(1-ethyl-2-methyl-indol-3-yl)-5-(4- diethylamino-2-ethoxy-phenyl)-5,7- dihydrofuro {3,4-b}-pyridine-7-one and record material containing it.

Description

1 GB 2 031 934 A 1

SPECIFICATION

Chromogenic pyridine compounds This invention relates to a chromogenic pyridine compound, and to record material having the compound 5 included in its colour-reactant system.

Chromogenic pyridine compounds of formula (1), ill R3 RS R3\ R5 10 -C C 4 R4/ 0 W R N C 1 9 ndlor C 2 11 R2 C 11 15 0 N 0 wherein R', R 2, R' and.11' are the same or different and each is a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, or a phenyl group, and R5 is a hydrogen atom, or an alkyl or alkoxy group having from 1 to 4 carbon atoms, include known compounds described in, for example, U.S. Patents 3 775 424 and 3 853 20 869 and Japanese Patent Application 48/53690. Such compounds are colourless materials which are capable of forming a colour when contacted with an appropriate acidic substance. Hence, they find utility in pressure-sensitive record material and mark-forming manifold systems.

The above-mentioned prior art also describes processes of preparing chromogenic pyridine compounds of formula (1) which generally start from quinolinic acid and comprise three discrete stages. In one such 25 process, quinolinic acid is first converted to the anhydride; 0 11 Stage II:- COGH Acetic ' C \ X 30 anhydride CC, XCOOH W" C 11 0 Then, quinolinic anhydride is reacted with an indole of formula (11) to give an isomeric mixture of keto acids of formula (111); 0 35 11 C---i47!kYC00H Stage 2:- 0 N W Q1,1_j it I C R2 40, + and/or 40 C N 0 11 R It 0 R2 0'K C il 0 0 C N 1 12 R 45 Finally, the desired chromogenic pyridine compound of formula (1) is obtained by condensing the keto acids of formula (111) with an aromatic amine of formula (IV) and rendering the resulting reaction mixture alkaline; Stage 3:- 0 11 C_ COOH R3 R4 N R 1 R2 + 6, R5 0 11 C_ "'N j HriMl (TV) N R2 R3 R5 \N \ - /i - - Y -1-TN 1:

R4 '/C N 1 R1 C 42 0 and for 3 R5 p \ h c- 1 ' U 1 R' C R2 -N 0 (m) (1) 2 GB 2 031934 A 2 (In the above formulae([[), (111), and (IV), R1, R 2, R 3, R 4 and R 5 areas defined for formula (1)). Hitherto, the keto acids used for reaction with the aromatic amine in the last stage of the process have always been removed from the reaction mixture of the previous, that is, the second, stage of the process. In each of the instances described in the above-mentioned prior art, the keto acids were collected by filtration, washed thoroughly, and even recrystallized to give a substance in a substantially uncontaminated or pure state. Only then were 5 the keto acids condensed with an aromatic amine.

The overall yield for this process can be up to 48% from quinolinic acid. However, according to the above-mentioned prior art, the yields for the second and third stages alone and separately are only about

48% and 58% respectively, giving an ov - erall yield of 28% from the quinolinic anhydride. When the yield for the first stage, is taken into account the 28% yield will drop even lower. The overall yields of the chromogenic 10 pyridine compounds of formula (1) are thus very low when such compounds are prepared by the above process.

It has now been found that a much better overall yield from quinolinic anhydride (and quinolinic acid) can be obtained for the chromogenic pyridine compound of formula (1) if the above-mentioned prior art process is carried out without removing the keto-acids of formula (111) from the reaction mixture of stage 2 and, preferably, without removing quinolinic anhydride from the reaction mixture of stage 1 as well. The resulting process is eminently suitable for being carried out in a single vessel and also in a continuous manner. This makes for a more convenient procedure and a reduced amount of reaction time and is unlike the above prior art process where, after each stage, the intermediates are actually removed from the reaction mixtures of stages 1 and 2, and only then are they washed and, in some instances recrystallised.

Accordingly, it is preferred to use a process of preparing a compound of formula (1), as hereinbefore defined, which comprises reacting quinolinic anhydride with an indole compound of formula (11), as hereinbefore defined, to give an isomeric mixture of keto acids of formula (111), as hereinbefore defined, and then, without removing the keto acids from the reaction mixture, reacting them with an aromatic amino compound of formula (IV), as hereinbefore defined, and adjusting the pH of the resulting reaction mixture to 25 at least 8.

The reaction between quinolinic anhydride and the indole compound of formula (11) is optimally carried out at a temperature of about 65 to 751C. Below about 65'C, a two phase mixture occurs whereas above this temperature a solution within which the reaction readily proceeds is obtained. Above 75'C, a disadvan tageous amount of by-products may be obtained.

Generally, the indole compound of formula (11) is present in excess, and the reaction with quinolinic anhydride is carried out for about 3 hours.

The reaction between the unisolated keto acids of formula (111) and the aromatic amino compound of formula (IV) is optimally conducted at a temperature of about 45 to 55'C, for example 50oC. Below 45'C, the reaction rate is too slow and above 55'C the keto acids may start to breakdown to form undesirable 35 by-products.

The reaction with the unisolated keto acids of formula (111) is advantageously carried out in the presence of acetic anhydride and for a time of about 4 hours.

The adjustment of the pH of the resulting reaction mixture to at least 8, i.e. to the alkaline side, is preferably carried out with sodium hydroxide which hydrolyses any acetic anhydride present and enables the formation of the lactone ring of the chromogenic pyridine compound of formula (1). If desired, the reaction mixture may first be diluted with water.

Adjustment of the pH to at least 8 precipitates the desired compound of formula (1) which may then be isolated from the reaction mixture by filtration to remove, for instance, any sodium acetate, and washing to remove other impurities. For example, an appropriate hydrocarbon wash can be used to removed any unreacted aromatic amine of formula (IV), whilst an aqueous-alkanol wash of appropriate proportions can be used to remove highly coloured undesired by-products. The alkanol used is preferably methanol, ethanol or isopropanol and may be employed in proportions of from 30 to 50% in water; however any proportion may be used so long as it is capable of removing the coloured by-products without dissolving excessive amounts of the pyridine compound of formula (1).

The process embraces the possibility of carrying out a washing operation on the keto acids, such as a siphon wash with, say, benzene or chlorobenzene. Such an operation is in fact advantageous since it removes any excess indole compound of formula (11), which may then be recovered, and also any of the useful chromogenic bis-indolyl pyridine compound of formula M; a.Nll-Rl Cr' R11 (V) 2 1 0 R2 wherein R' and R 2 are as defined forformula (1), which may have been produced as a by-product. If the excess indole compound of formula (11) is not removed, then it may in the subsequent stage of the process compete with the isomeric keto acids of formula (111) for reaction with the aromatic amine of formula (IV). 65 Thus, the inclusion in the process of a washing operation on the keto acids of formula (111) gives an even 3 GB 2 031934 A 3 further improvement in the overall yield and also enables the convenient removal of the chromogenic by-product.

One of the starting materials, quinolinic anhydride may be prepared from a reaction between commercially available quinolinic acid and acetic anhydride in accordance with the first stage of the prior art process. It is preferred however that the resulting quinolinic anhydride is not removed from the reaction mixture before its subsequent reaction with an indole compound of formula (11).

The preparation of quinolinic anhydride is conveniently carried out at a temperature of about 120 to 1300C. The reaction does not proceed at a satisfactory rate below 120'C whereas an upper limit of 1130'C is appropriate because of the fact that the boiling point of acetic anhydride is reached at 1400C.

Acetic anhydride is desirably used in excess of quinolinic acid and the time required to complete the reaction is usually from 10 to 20 minutes.

The process includes the possibility of carrying out a washing operation on the resulting quinolinic anhydride, particularly a carbon tetrachloride siphon wash, in order to remove any acetic acid and unreacted acetic anhydride. The removal of the latter compound may be desirable since its presence in the next reaction stage would facilitate the production of a greater amount of the chromogenic bis-indolyl pyridine 15 compound of formula (V).

The chromogenic pyridine compound of formula (1) which constitutes the present invention is that wherein R 2, R'and R 4 are each ethyl, R' is methyl and R' is ethoxy. It is a novel compound existing as the isomers disclosdd in the example below.

The compounds of formula (1) are useful, usually as a mixture of the obtained isomers, as colour forming 20 components in carboniess copy paper and other record materials. Systems of such components are well known in the art, for example, as disclosed in U.S. Patents 3 775 424,3 853 869 and 3 627 581, and the compounds prepared by the process of the present invention may be used as the colourless chromogenic compound in such systems.

The following is an example of the preparation of the compound of the present invention. Unless 25 otherwise noted, the percentages therein are by weight.

EXAMPLE

In a 100-mi round bottom flask are placed 5.01 g (0.03 mole) of 2,3pyridinedicarboxylic acid (quionlinic acid) and 9 ml. (0.06 mole) of acetic anhydride. A clear solution results upon heating at 120-130'C. for 20 minutes. On cooling, as soon as crystallization starts, 60 ml. Of CC14 is added. The mixture Of CC14 acetic anhydride and acetic acid is siphoned off. Three additional CC14 (10 ml. each) washes were made.

Added to the solid in the reaction flask is 6.88 g (0.0433 mole) of 1 ethyl-2-m ethyl i ndol e. The mixture is maintained at 65-701C for 3 hours. A solid-liquid stirrable mixture is present during this time. To the cooled reaction mixture is added 50 mi. of benzene (or chlorobenzene). The benzene and soluble components are 35 siphoned off and two additional 15 ml. washes are made.

To the keto acids remaining in the reaction flask are added 4.63 g. (0. 0240 mole) of N,N-diethyl-m-phene ticline and 32 ml. of acetic anhydride. After 4 hours at 55'C., the reaction slurry is poured into 28 g. of sodium hydroxide in 250 mi. of water. The precipitated product is stirred for one hour at 50C. The product is filtered and then washed several times with water, 20 ml. of 30% methanol-water and finally with 15 mi. of 40 petroleum ether (60-1 10oQ. The overall yield of the isomeric chromogenic compounds, (7-(l-ethyl-2 methylindol-3-yl)-7-(4-diethyl-amino-2-ethoxyphenyl)-5,7-dihydrofuro 13,4bl-pyridine-5-one and 5-(l-ethyl 2-methylindol-3-yl)-5-(4-diethylamino-2-ethoxyphenyl)-5,7-dihydrofuro 13, 4-bl-pyridine-7-one, is 74% based on the amount of starting pyridine-2,3-dicarboxylic acid. The ratio of said isomers in the product is about 20 to 1, respectively. In addition, the overall yield from 2,3-pyridine dicarboxylic acid anhydride was experimentally determined as about 86%, and the isolated yield of the bis- indolyl pyridine compound produced as a by-product was 7.8%.

The present application is divided from application No. 37972/78 to methods of preparing compounds of Formula 1, compounds so prepared and record materials containing them. We disclaim herein the compound of the present invention when prepared by a method claimed in application No. 37972/78 and record material 50 containing it.

Claims

1. The compound 7-(l-ethyl-2-methyl-indol-3-yi)-7-(4-diethylamino-2ethoxy-phenyl)-5,7-dihyd rofuro 55 13,4-bl-pyridine-5-one and/or 5-(l-ethyl-2-methyl-indol-3-yl)-5-(4- diethylamino-2-ethoxy-phenyl)-5,7dihydrofuro 13,4-bl-pyridine-7-one.

2. A record material comprising as a colour former the compound of claim 1.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon Surrey, 1980.

Published by the Patent Office, 25 Southampton Buildings, London, WC2A 'I AY, from which copies may be obtained.