US3491116A - 3-(phenyl)-3-(indol-3-yl)-phthalides - Google Patents

Description

Jan. 20, 1970 AQ-HAN 3,491,116

5-(PHENYL)-'5-( IlIDOL--$--YL) -PHTHALIDE3 Filed Jan. 59, 1967 FIG. I

BASE-SHEET OF RECORD MATERIAL COATED ON THE REAR WITH MINUTE PRESSURE-RUPTURABLE CAPSULES CONTAINING LIQUID SOLUTION OF CHROMOGENIC MATERIAL DEVELOPABLE ON CONTACT WITH AN ELECTRON- ACCEPTING MATERIAL OF THE LEWIS- ACID TYPE TO COLORED FORM.

RECEIVING SURFACE OF UNDERSHEET COATED WITH AN ELECTRON-ACCEPTING MATERIAL OF THE LEWIS-ACID TYP INVENTOR CHAO-HAN LIN HIS ATTORNEYS United States Patent 3,491,116 3-(PHENYL)-3-(INDOL-3-YL)-PHTHALIDES Chao-Han Lin, Dayton, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Jan. 30, 1967, Ser. No. 612,459 Int. Cl. (107d 99/04; B411 1/36 US. Cl. 260-32614 8 Claims ABSTRACT OF THE DISCLOSURE A novel chromogenic material of normally colorless form, having a structural formula:

wherein R and R comprise alkyl radicals having from one to five carbon atoms, aryl radicals, and hydrogen; and R and R comprise alkyl radicals having from one to five carbon atoms and hydrogen; said material assuming a colored form upon contact with a Lewis acid molecule. Examples include This invention pertains to novel chromogenic com pounds for use in pressure sensitive record material and to an improved mark-forming manifold system incorporating these novel chromogenic compounds. More specifically, this invention pertains to 3-dialkylaminophenyl-3- indolyl phthalides which have the form of substantially colorless, i.e. white, or slightly colored solids, or approach being colorless when in liquid solution, but which may be converted to dark-colored forms upon reactive contact with acidic material. As used in mark-forming systerns, marking in desired areas on support webs or sheets may be accomplished by effecting localized reactive ,contact between the chromogenic material and the acidic material on or in such a web or sheet, such material being brought thereto by transfer, or originally there in situ, the desired reactive contact forming dark-colored materials in the intended image areas.

Pressure-sensitive, mark-forming systems of the prior art include that disclosed in application for Letters Patent No. 392,404, filed Aug. 27, 1964, by Robert E. Miller and Paul S. Phillips, Jr., and now abandoned. The latter application provides a marking system of disposing on and/ or within sheet support material the unreacted markforming components (at least one of which is a polymeric material) and a liquid solvent in which each of the markforming components is soluble, said liquid solvent being present in such form that it is maintained isolated by a pressure-rupturable barrier from at least one of the markforming components until the application of pressure causes a breach or rupture of the barrier in the area delineated by the pressure pattern. The mark-forming components thereby are brought into reactive contact, producing a distinctive mark.

It is an object of this invention to provide new and improved substances having chromogenic properties which may be incorporated in a web or coated onto the surface of a web to provide a novel manifolding unit, and which are useful in carrying out improved methods of marking involving reactive contact with a color-activating material to develop dark-colored materials in areas where marking is desired.

It is another object of this invention to provide modified compounds, based upon the 3-(p-dialkylaminophenyl)-3-indolyl phthalides, which are substantially colorless, or slightly colored offering a new and improved variety of chromogenic characteristics, and developing novel dark-colored substances upon contact with coloractivating materials.

It is a further object of this invention to provide a new and improved mark-forming system which has the form of disposing within a web or upon the surface of a web or sheet support material unreacted chromogenic material which is capable of being reactively contacted with an acidic material to produce a dark-colored substance, thus providing marks having desirable color intensity and hue.

In accordance with this invention, there is provided a novel, substantially colorless or slightly colored, chromogenic compound having the structural formula:

wherein R and R comprise alkyl radicals havingfrom 1 to 5 carbon atoms, aryl radicals, and hydrogen; and R and R comprise alkyl radicals having from 1 to 5 carbon atoms and hydrogen. Examples of these novel compounds are 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl) phthalide having the structural formula:

3 3 (p dimethylaminophenyl) 3 (2 methylindol 3- yl) phthalide having the structural formula:

3 (p di n b utylaminophenyl 3 (1,2 dimethylindol-3-yl) phthalide having the structural formula:

3-(p-di n butylaminophenyl)-3-(2-methylindol-3-yl) phthalide having the structural formula:

CH I

3 (p dimethylaminophenyl) 3 (2-phenylindol-3-yl) 3-(p-dimethylaminophenyl)-3-(1-methyl-2 phenylindol- 3-yl) phthalide having the structural formula:

3 (p diethylaminophenyl) 3 (2 phenylindol-S-yl) phthalide having the structural formula:

I 20 Al}; N 7 O In accordance with another feature of this invention a new composition of matter comprises the dark-colored substance having a resonant form developed by contact of a color-activating material with one of the above-mentioned chromogenic compounds. The color-developing or activating material is an acidic substance for converting the chromogenic compound to the resonant form.

The method of marking of this invention, i.e., by developing a dark-colored material from substantially colorless or slightly colored chromogenic compounds comprises providing a chromogenic compound selected from among the above-mentioned compounds and bringing such chromogenic compound into reactive contact in areas where marking is desired with an acidic color-activating substance to produce a dark-colored resonant form of the chromogenic compound by the action thereon in said areas of the said acidic substance.

The acidic materials employed in this invention can be any compound within the definition of a Lewis acid, i.e., an electron acceptor. Preferably, acidic organic polymers such as phenolic polymers are employed as the acidic material. The novel chromogenic materials exhibit the advantage of improved color stability when reacted with such phenolic polymers. The solution formation of the solid particles of polymeric material in the same solvent with the substantially colorless chromogenic compounds allows penetration of the color into the support sheet, if porous,-e.g., paper, so that the colored form of the chromogenic material sinks into the body of the sheet and is not merely on the surface of the sheet. This feature protects against erasure of recorded data by attrition of the surface of the record sheet.

Reference is directed to the drawings. FIGURE 1 is a diagrammatic representation of a two-sheet unit manifold, a perspective in which the bottom surface of the overlying is supplied on the surface or near it with a multiplicity of minute pressure-rupturable microcapsules, each containing a droplet. Each droplet contains a solution of the basic chromogenic component. An acidic component, such as an acid clay or a phenolic polymeric material lies Within the lower web or sheet or upon the upper surface of the lower Web or sheet. A colored mark is made by the use of a stylus, a type character, or other pressure-writing means applied to the two-sheet unit manifold.

The encapsulated droplets are released on the rupture of the capsules in writing operations, as shown in FIGURE 10!. The liquid of the released droplets is transferred in the pattern of the data configuration to the top of the underlying sheet. The top of the underlying sheet is coated or impregnated with a material reactant with the chromogenic material, e.g., a phenolic polymer material having an acid-reacting OH group. The drawings show capsules on the over-sheet containing a liquid solution of chromogenic material. However, the capsules can contain the polymeric phenolic material in liquid solution and the top surface of the under-sheet may be supplied with the chromogenic material in particulate form. The improvement in the system is the chromogenic compound which is the novel substance of the instant invention.

Referring again to FIGURE 1 comprising an upper web or sheet having the chromogenic material dispersed within or upon in a contiguous juxtaposition, it is possible to incorporate the chromogenic material in a solid, crystallinestate in a binder material so that the chromogenic material may be transferred from the upper Web or sheet upon the application of pressure from a stylus to deposit some of the chromogenic material on a surface carrying a color activating polymeric material. Preferably, the chromogenic substance is dissolved in a solvent and minute droplets of the solution of the chromogenic material are encapsulated in minute, rupturable capsules. Obviously, many other arrangements, configurations and relationships of the solvent and the mark-forming materials, with respect to their encapsulation and location on the supporting sheet or webs can be envisioned. Such arrangements are thoroughly described in the aforementioned application Ser. No. 392,404 to Miller et al., and need not be repeated herein.

It is noted that the polymeric mark-forming components should have a common solubility with the chromogenic material in at least one liquid solvent when the acid-reacting material is a phenolic or other organic acidic polymer. It is also noted that in a single system several chromogenic materials may be used with the same or different polymeric materials. Several polymeric materials can be reactively contacted With a single chromogenic compound or with a mixture of chromogenic compounds.

As mentioned above, the solvent is maintained in physical isolation in minute droplets until such time as it is released by application of pressure. This may be accomplished by several known techniques, but preferably isolation is maintained by individual encapsulation of the solvent droplets in a microcapsule according to the procedures described, for example, in U.S. Patent No. 2,712,507, issued to Barrett K. Green on July 5, 1955; 2,730,457 issued to Barrett K. Green and Lowell Schleicher on Jan. 10, 1956; 2,800,457, issued to Barrett K. Green and Lowell Schleicher on July 23, 1957; and 2,800,458, issued to Barrett K. Green on July 23, 1957, reissued as Reissue Patent No. 24,899 on Nov. 29, 1960. The microscopic capsules, when disposed within or upon a supporting web as a multiplicity in contiguous juxtaposition, are rupturable by pressure, such a normal marking pressures utilized, for example, in writing or typing operations.

The material or materials chosen as the wall material of the microcapsule, in addition to being pressure rupturable, must be inert or unreactive in respect to the contents of the capsule and the other mark-forming components so that the wall material remains intact under normal storage conditions until such time as it is released by the application of marking pressure. Examples of such wall materials are gelatin, gum arabic and many others thoroughly described in the aforementioned patents.

For use in record material, the capsule size should not exceed 50 microns in diameter. Preferably, the capsules should be smaller than microns in diameter.

The acidic organic polymeric material useful in this invention include phenolic polymers, phenol acetylene polymers, maleic acid-rosin resins, partially or wholly hydrolyzed styrene-maleic anhydride copolymers and ethylene-maleic anhydride copolymers, carboxy polymethylene and wholly or partially hydrolyzed vinyl methyl ether maleic anhydride copolymer and mixtures thereof.

Phenolic polymers found useful include alkyl-phenolacetylene resins, which are soluble in common organic solvents and possess permanent fusibility in the absense of being treated by cross-linking materials. A specific group of useful phenolic polymers are members of the type commonly referred to as novolacs (as sold by Union Carbide Corp., New York, N.Y.), which are characterized by solubility in common organic solvents and which are, in the absence of cross-linking agents, permanently fusible. Generally, the phenolic polymer material found useful in practicing this invention is characterized by the presence of free hydroxyl groups and the absence of groups such as methylol, which tend to promote infusibility or cross-linking of the polymer, and by their solubility in organic solvents and relative insolubility in aqueous media. Again, obviously, mixtures of these organic polymers and other acidic materials can be employed.

Resoles, if they are still soluble, may be used, though subject to change in properties upon aging.

A laboratory method useful in the selection of suitable phenolic resins is the determination of the infra-red absorption pattern. It has been found that phenolic resins showing an absorption in the 3200-3500 cm? region (which is indicative of the free hydroxyl groups) and not having an absorption in the 16004700 cm. region are suitable. The latter absorption region is indicative of the desensitization of the hydroxyl groups and, consequently, makes such groups unavailablefor reaction with the chromogenic materials.

The preparation of organic polymeric materials for practicing this invention is described in Industrial and Engineering Chemistry, vol. 43, pages 134 to 141, January 1951, and a particular polymer thereof is described in Example I of U.S. Patent No. 2,052,093, issued to Herbert Honel on Aug. 25, 1936, and the preparation of the phenol-acetylene polymers is described in Industrial and Engineering Chemistry, vol. 41, pages 73 to 77, January 1949.

The preparation of the maleic anhydride copolymers is described in the literature, such as, for example, one of the maleic anhydride vinyl coploymers, as disclosed in the publication, Vinyl and Related Polymers, by Calvin E. Schildknecht, second printing, published April 1959, by John Wiley & Sons, Incorporated. See pages to 68 (styrene-maleic anhydride copolymer), 628 to 630 (vinyl methyl ether-maleic anhydride copolymer), and 530 to 531 (ethylene-maleic anhydride copolymer).

When the acidic material is one of the aforementioned organic polymers, the liquid solvent chosen must be capable of dissolving the mark-forming components. The solvent may be volatile or non-volatile, and a single or multiple component solvent may be used which is wholly or partially volatile. Examples of volatile solvents useful in the afore-described basic chromogen-acidic polymer are toluene, petroleum distillate, perchloroethylene, and xylene. Examples of non-volatile solvents are high-boiling point petroleum fractions and chlorinated biphenyls.

Generally, the solvent chosen should be capable of dissolving at least 0.3%, on a weight basis, of the chromogenic material, and about a 3-5 on a weight basis, of the polymeric material to form an eflicient reaction. However, in the preferred system, the solvent should be capable of dissolving an excess of the polymeric material, so as to provide every opportunity for utilization of the chromogenic material and, thus, to assure the maximum coloration at a reaction site.

A further criterion of the solvent is that it must not interfere with the mark-forming reaction. In some instances, the presence of the solvent may interfere with the mark-forming reaction or diminish the intensity of the mark, in which case the solvent chosen should be sulficiently vaporizable to assure its removal from the reaction site after having, through solution, brought the markforming components into intimate admixture, so that the mark-forming contact proceeds.

Since the mark-forming reaction requires a intimate mixture of the components to be brought about through solution of said components, one or more of the markforming components may be dissolved in the isolated solvent droplets, the only requirement being that at least one of the components essential to the mark-forming reaction be maintained isolated until reactively contacted with the other.

In the usual case, the mark-forming components are so chosen as to produce a mark upon application of pressure at room temperature (20 to 25 degrees centigrade). However, the present invention includes a system in which the solvent component is not liquid at temperatures around room temperature but is liquid and in condition for forming solutions only at elevated temperatures.

The support member on which the components of the system are disposed may comprise a single or dual sheet assembly. In the case where all components are disposed on a single sheet, the record material is referred to as a self-contained system. Where there must be a migration of the solvent, with or without mark-forming component, from one sheet to another, the record material is referred to as a transfer system. (Such a system may also be referred to as a two-fold system, in that at least two sheets are required and each sheet includes a component, or components, essential to the mark-forming reaction.) Where a copious amount of the colored reaction product in liquid form is produced on a surface of one sheet, it may produce a mark by transfer to a second sheet as a colored mark.

In the preferred case, where microcapsules are employed, they may be present in the support material either disposed therethroughout or as a coating thereon, or both. The capsules may be applied to the sheet material while still dispersed in the liquid vehicle in which they were manufactured, or, if desired, separated and the separated capsules thereafter dispersed in a solution of the polymeric component (for instance, 30 grams of water and 53 grams of a 1% aqueous solution of polyvinyl methyl ether maleic anhydride) to form a coating composition in which, because of the inertness of the solution and the capsules, both retain their identity and physical integrity. When this composition is disposed as a film on the support material and dried, the capsules are held therein subject to rupture to release the liquid contained. This latter technique, relying on the inertness of the microcapsule and the dispersing medium of the film-forming markforming component, allows for a method of preparing a sensitive record coating with the capsules interspersed directly in a dry film of the polymeric material as it is laid down from the solution. A further alternative is to disperse in a liquid medium one or more mark-forming components, insoluble therein, and disperse in said medium the insoluble microcapsules, with the result that all components of the mark-forming system may be disposed on or Within the support sheet in the one operation. Obviously, the several components may be applied individually.

The respective amounts of the several components will vary, depending primarily upon the nature of the materials and the architecture of the record material unit. Suitable lower amounts include, in the case of the chromogenic material, about .005 to .075 pound per ream (a ream in this application meaning five hundred (500) sheets of 25" x 38" paper, totalling 3,300 square feet); in the case of the solvent, about 1 to 3 pounds per ream; and in case of the polymer, about /2 pound per ream. In all instances, the upper limit is primarily a matter of economic consideration.

In the instance where the mark-forming components are interspersed throughout a single support sheet material (so-called self-contained unit), the following technique or procedure has been found useful:

The slurry of capsules may be applied to a wet web of paper as it exists on the screen of a Fourdrinier paper machine, so as to sink the paper web a distance depending on the freeness of the pulp and the water content of the web at the point of application.

The capsules may be placed directly in the paper or in a support sheet. Not only capsule structures, but films which hold a multitude of droplets for local release in an area subject to pressure may be utilized. (See US. Patent No. 2,299,694 which issued Oct. 20, 1942, to B. K. Green.)

With respect to the acidic organic polymeric component, a solution thereof in an evaporable solvent is introduced into twice as much water and agitated while the evaporable solvent is blown off by an air blast. This leaves an aqueous colloidal dispersion slurry of the polymeric material, which may be applied to the paper so as to leave a surface residue, or the slurry may be applied to paper at the size-press station of a papermaking machine by roller. In another method of making a polymersensitized sheet, the water-insoluble polymer is ground to the desired particle size in a ball mill with water, preferably with a dispersing agent, such as a small quantity of sodium silicate. If a binder material of hydrophilic properties is ground with the phenolic material, the binder itself may act as a dispersant. If desired, an amount of binder material of up to 40%, by weight, of the employed amount of the polymeric material may be added to the ball-milled slurry of materials, such binder materials being of the paper coating binder class, including gum arabic, casein, hydroxyethylcellulose, and latex (such as styrene-butadiene copolymer). If desired, oil adsorbents in the form of fullers earths may be added to the polymeric material particles to assist in retaining, in situ, the liquid droplets to be transferred to it in data-representing configuration, for the purpose of preventing bleeding of the print.

Another way of applying the chromogenic or polymeric material individually to a single sheet of paper is by immersing a sheet of paper in a 1% to solution of the material in an evaporable solvent. Obviously, this must be done alone for each reactant, because if the other reactant material were present, it would result in a premature coloration over the sheet area. A dried sheet with one component then may be coated with a solution of the other component, the solvent of which is a non-solvent to the already supplied component.

The polymeric material may be dissolved in ink composition vehicles to form a printing ink of colorless character and, thus, may be used to spot-print a proposed record sheet unit sensitized for recording in a reactionproduced color in those areas by application of a solution of the chromogenic material.

In the case of phenolic polymer, a printing ink may be made of up to 75% weight, of the phenolic polymeric material in a petroleum solvent to a viscosity suitable for printing purposes. The relative amounts of components to be used are the most convenient and economical amounts consistent with proper visibility of the recorded data. The resolution of the recorded data is, among other things, dependent on particle size, distribution and amount of particles, liquid solvent migration, chemical reaction efficiency, and other factors, all of which are things that may be worked out empirically by one familiar with the art, and which do not determine the principle of the invention, which, in part, involves means for enabling the bringing into solution, by marking pressure, of two normally solid components in a common liquid solvent component held isolated as liquid droplets, preferably in marking-pressure-rupturable capsules having film walls, or else held isolated in a continuous marking-pressurerupturable film as a discontinuous phase.

In the base-acid color system of this invention the acidic mark-forming component'(s) reacts with the basic chromogenic material(s) to effect distinctive color formation or color change. In a multi-sheet system in which an acidic organic polymer is employed, it is desirable to include other materials to supplement the reactants. For example, kaolin can be added to improve the transfer of the liquid and/or the dissolved materials between the sheets. In addition, other materials such as bentoni-te, atta-pulgite, talc, feldspar, halloysite, magnesium trisilicate, silica gel, pyrophyllite, zinc sulfate, zinc sulfide, calcium sulfate, calcium citrate, calcium phosphate, calcium fluoride, barium sulfate and tannic acid can be included.

Various methods known to the prior art and disclosed in the aforementioned application Ser. No. 392,404 to Miller, et a1. and US. patent application Ser. No. 420,193 to Phillips et al. now US. Patent 3,431,494, can be employed in coating compositions of the mark-forming materials into their supporting sheets. An example of the compositions which can be coated onto the surface of an underlying sheet of a two-sheet system to react with the capsule coating on the underside of an overlying sheet is as follows:

Coating composition: Percent by wt.

Phenolic polymer mixture 17 Papr coating kaolin (white) 57 Calcium carbonate 12 Styrene butadiene latex 4 Ethylated starch 8 Gum arabic 2.

EXAMPLE I Preparation of 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl) phthalide.

An intermediate keto-acid, 4'-dimethylaminobenzophenone-Z-carboxylic acid was prepared as herein set forth:

A mixture of 14.5 grams of dimethy laniline and 14.8 grams of phthalic anhyd-ride in 30 milliliters of benzene was stirred in a flask under ice-cooling. To the mixture,

26.0 grams of anhydrous aluminum chloride was slowly added. Stirring was continued at room temperature for 40 minutes and at 55-60 C. for 30 minutes. Upon cooling to room temperature, the benzene solvent was removed by extraction with petroleum ether, and the residue was decomposed with 34 milliliters of 17% sulfuric acid. After partial neutralization with about milliliters of concentrated ammonium hydroxide, the sulfuric acid solution was diluted with water to a volume of 900 milliliters and stirred for an additional 30 minutes. The precipitate formed was removed by filtration, and exhibited a weight of 13.5 grams and a melting point of 195-200 C. The crude intermediate was recrystallized from dilute sulfuric acid, thereupon exhibiting a melting point of 200-203 C.

The preparation of 3-(p-dimethylaminophenyl)-3-(1,2- -dimethylindol-3-yl) phthalide was effected by the following process:

The keto-acid, prepared in the process set forth above was used in this preparation. 5.4 grams of 4'-dimethylaminobenzophenone-2-carboxylic acid and 3.2 grams of 1,2dimethylindole were mixed with twenty milliliters of acetic anhydride. After being heated for fifteen minutes to near the boiling point on a hot plate, the reaction mixture was poured into one hundred milliliters of water and heated for an additional ten minutes. Upon cooling, the mixture was treated with ammonium hydroxide until it was strongly alkaline, then stirred for ten minutes. The solid which exhibited a weight of 7.8 grams, was removed by filtration purified by recrystallization from a benzene solution.

The purified product exhibited a melting point of 226- 228 C. A solution of the product in benzene turned a vivid blue when applied to a paper sheet coated with a phenolic polymer, but imparted a blue-purple color to paper coated with attapulgite clay.

EXAMPLE II The preparation of 3-(p-dimethylaminophenyl)-3-(2- methylindol-3-yl) phthalide was effected in the following process:

5 .4 grams of the 4'-dimethylaminobenzophenone-2- carboxylic acid prepared in the foregoing procedure, were mixed with 2.9 grams of 2-methylindole and 20 milliliters of acetic anhydride and heated to the boiling point of the mixture on a hot plate for fifteen minutes. A product was isolated according to the procedure described in Example I. The product exhibited a weight of 8.6 grams and was purified by recrystallization from benzene. The purified product exhibited a melting point of 211-212 C. The color of the product when dissolved in benzene and reacted with paper coated with phenolic polymer was blue.

EXAMPLE III The compound 3-(p-di-nbutylaminophenyl)13-(1,2-di' methylindol-3-yl) phthalide was prepared in the following procedure:

24.6 grams of di-n-butylaniline, 14.8 grams of phthalic anhydride, and 20 milliliters of benzene were stirred in a 100 milliliter flask immersed in a cold water bath. 26.7 grams of aluminum chloride was slowly added, the addition requiring ten minutes. The water bath temperature was raised to 50 C. in thirty minutes, and maintained at 50 C. to 54 C. for one hour. The water bath was removed and the flask cooled to room temperature. The reaction mixture was then decomposed with 150 milliliters of 20% sulfuric acid, resulting in the formation of an oil floating as a supernatant layer. 400 milliliters of water were added, causing the oil to change to a semi-solid phase. the aqueous solution was decanted and the semisolid material was washed twice with 400 milliliter quantities of water.

The semi-solid material was then stirred with 1200 milliliters of water for one hour. The semi-solid material disintegrated into a light-green colored precipitate. The water was decanted and fresh water added. After three hours a powdered solid product was percipitated exhibiting a weight of 18.4 grams and a melting point range of 164-168 C. 5 grams of the solid intermediate product, 4-di-n-butylaminobenzophenone 2 carboxylic acid was dissolved in 50 milliliters of toluene, treated with charcoal and filtered. A yellow filtrate was treated with an equal volume of petroleum ether yielding a yellow precipitate exhibiting a weight of 4.7 grams and a melting point range of 168170 C.

1.06 grams of the 4'-di-n-butylaminobenzophenone-Z- carboxylic acid product of the foregoing procedure, 0.44 grams of 1,2-dimethylindo1e and 10 milliliters of acetic anhydride were heated in a thirty milliliter beaker to a temperature slightly below the boiling point of the mixture for 15 minutes. The reaction mixture was poured into milliliters of water, made alkaline by the addition of ammonium hydroxide, and stirred for two hours. A product precipitated which exhibited a weight of 1.3 grams. The product, 3-(p-di-n-butylaminophenyl) 3 (1,2 dimethylind0l-3-yl) phthalide was dissolved in 30 milliliters of benzene, treated with activated charcoal, and filtered. The filtrate was concentrated to 5 milliliters and further purified to yield a purified product exhibiting a weight of 1.05 grams and a melting point range of 140-141.5 C. A benzene solution of the product appeared purple when contacted with attapulgite clay coated on paper and blue when contacted with phenolic polymer coated on paper.

EXAMPLE IV Preparation of 3-(p-di-n butylaminophenyl)-3-(2-methylindol-3-yl) phthalide.

3.5 grams of the intermediate 4'-di-n-butylaminobenzophenone-2-carboxylic acid, prepared as described in Example III, 1.3 grams of 2-methylindole, and 25 milliliters of acetic anhydride were heated to boiling for 15 minutes, poured into 125 milliliters of Water, made alkaline with ammonium hydroxide and stirred for minutes. A precipitate was separated and purified, repeatedly, from a mixture of benzene and petroleum ether. A product thus obtained melted at 157.5159.5 C. A benzene solution of the product turned a purple color when contacted with attapulgite clay coated on paper but blue when contacted with a phenolic resin coated on paper.

EXAMPLE V The preparation of 3-(p-dimethylaminophenyl)-3-(2- phenylindol-3-yl) phthalide was effected by the following process:

2.7 grams of 4' dimethylaminobenzophenone 2 carboxylic acid prepared in the procedure set forth in Example I was mixed With 2.1 grams of 2-phenylindole and forty milliliters of acetic anhydride. A crude product, weighing 4.4 grams, was isolated according to the procedure described in Example I. The product was recrystallized from the benezene solution. The purified product exhibited a melting point of 252-253 C. The benzene solution of the product imparted a green color to paper coated with a phenolic polymer.

EXAMPLE VI The preparation of 3-(p dimethylaminophenyl 3 (1- methyl-Z-phenylindol-3-yl) phthalide was effected by the following procedure.

0.8 gram of 4 dimethylaminobenzophenone 2 carboxylic acid prepared in the procedure set forth in Example I, 0.62 gram of 1-methyl-2-phenylindole and 5 milliliters of acetic anhydride were reacted as set forth in Example III. Following the isolation procedure of Example III, a crude product weighing 1.0 gram was obtained upon recrystallization from 95% ethanol, a pure product exhibiting a melting point range of 146 C. to 148 C. was obtained. A solution in benzene of the 3-(pdimethylaminophenyl)-3 (1 methyl-Z-phenylindol-3-yl) phthalide product appeared a blue color when reacted with attapulgite clay coated on paper and appeared green when contacted witha phenolic polymer coated onto paper. when contacted with a phenolic polymer coated onto paper.

EXAMPLE VII The compound 3-(p-diethylaminophenyl)-3-(2-phenylindol-3-y'l) phthalide was prepared in the following procedure:

An intermediate keto-acid 4-diethylaminobenz0phenone-Z-carboxylic acid was first prepared by stirring 18.0 grams of diethylaniline, 14.8 grams of phthalic anhydride, and 20 milliliters of benzene in a 100 milliliter flask immersed in a cold water bath. 26.7 grams of aluminum chloride was slowly added to the reaction mixture, the addition requiring 12 minutes. The water bath temperature was raised to 52 C. over a period of thirty minutes and maintained at 52-55 C. for 7 minutes. Twenty milliliters of water were added, followed by the addition of 200 milliliters of 20% sulfuric acid to the reaction mixture. Upon heating a turbid solution was observed. The solution was diluted with water to 800 milliliters and neutralized with ammonium hydroxide to a pH of 1.8. A semi-solid phase appeared and was separated and stirred into an 800 milliliter quantity of water for 120 minutes. A solid precipitate was formed which exhibited a weight of 15.7 grams and a melting point range of 173-177 C. The crude material was purified by dissolving said material in 4 normal sulfuric acid, filtering the solution to remove insoluble material, and reprecipitating the product with ammonium hydroxide. The melting point of the 4'-diethylaminobenzophenone-2-carboxylic acid intermediate was thereby raised to 180181 C.

The intermediate keto-acid prepared in the foregoing procedure was used in the preparation of the compound 3-(p diethylaminophenyl)-3-(2-phenylindol-3-yl) phthalide by heating 0.74 grams of 4-diethylaminobenzophenone-2-carboxylic acid, 0.48 grams of 2-phenylindole and 15 milliliters of acetic anhydride in a beaker over a hot plate for 15 minutes. The reaction mixture was poured into 100 milliliters of water, made alkaline with ammonium hydroxide and stirred for 60 minutes. A crude product exhibiting a weight of 1.1 grams was precipitated. The crude product was dissolved in 50 milliliters of benzene, treated with charcoal and filtered. The filtrate upon standing yielded a 3-(p-diethylaminophenyl)-3-(2-phenylindo1-3-yl) phthalide product exhibiting a melting point of 246247 C. A benzene solution of the product appeared a blue-green color when contacted with attapulgite clay coated on paper and a green color when contacted with a phenolic olymer coated on paper.

12 What is claimed is: 1. A chromogenic compound having the structural formula where R and R consist of alkyl having from one to four carbon atoms, phenyl, and hydrogen; and Where R and R consist of alkyl having from one to four carbon atoms, and hydrogen.

2. The chromogenic compound of claim 1 where R R R and R are methyl, said compound being 3-(=pdimethylaminophenyl) 3 (1,2 dimethylindol 3- yl) phthalide.

3. The chromogenic compound of claim 1 where R is hydrogen and R R and R are methyl, said compound being 3 (p dimethylaminophenyl) 3 (2- methylindol-3-yl) phthalide.

4. The chromogenic compound of claim 1 where R and R are methyl and R and R are n-butyl said com pound being 3 (p di n butylaminophenyl)-3-(1,2- dimethylindol-3-yl) phthalide.

5. The chromogenic compound of claim 1 where R is hydrogen, R is a methyl, and R5 and R are n-butyl, said compound being 3-(p di-n-butylaminophenyl)-3-(2- methylindol-3-yl) phthalide.

6. The chromogenic compound of claim 1 Where R is hydrogen, R is a phenyl, and R and R are methyl, said compound being 3-(p-dimethylaminophenyl)-3-2- phenylindol-3-yl) phthalide.

7. The chromogenic compound of claim 1 where R is a phenyl, and R R and R are methyl, said compound being 3-(p-dimethylaminophenyl) 3 (1 methyl-2- phenylindol-3-yl) phthalide.

8. The chromogenic compound of claim 1 where R is hydrogen, R is a phenyl; and R and R are ethyl, said compound being 3 (p diethylaminophenyl) 3 (2- phenylindol-3-yl) phthalide.

References Cited UNITED STATES PATENTS 2,505,486 4/1950 Green 260-3433 XR ALEX MAZEL, Primary Examiner J. A. NARCAVAGE, Assistant Examiner Us; 01. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 491, 116 Dated: January 20, 1970 Inventor: Chao-Han Lin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 10, 'butylaminophenyl'' should be -buty1aminopheny1)--. Column 6, line 36, "a" should be -an--. Column 8, line 47, "3, 431, 494" should be --3, 455, 721--; line 57, "Papr' should be "Paper-a Column 9, line 56, "13-" should be -3- Column 10, line 5, 'percipitated" should be --preci'pitated-; line 8, "4" should be --4'--; line 61, "benezene' should be --benzene-. Column 11, line 8 should be deleted. Claim 6,

line 3, "3-2" should be 3-(2 SIGNED AN'D SEALED JUL? 1970 (SEAL) Attest:

Edward M. Fletcher, I L

WILLIAM E. 50mm, .13. Ammng Offmer comissioner of Patents

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