Bis-quinizarin compounds are disclosed. They have the structure: ##STR1## where X is ##STR2## --CF.sub.2 --, or a bond.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
The invention relates to certain bis-quinizarin compounds and methods for 
their preparation. 
(b) Description of the Prior Art 
Quinizarin is a known compound whose synthesis is reported in Organic 
Synthesis, Collective Volume I, page 476. To the best of the applicants' 
knowledge, bis-quinizarin compounds are not reported in the literature. 
SUMMARY OF THE INVENTION 
The products of the invention are bis-quinizarin compounds having the 
structure: 
##STR3## 
where X is 
##STR4## 
or a bond. The preferred product of the invention is 6,6'-carbonyl 
bis-quinizarin which has the structure: 
##STR5## 
The invention also includes a process for preparing bis-quinizarin 
compounds in which an aromatic tetracarboxylic acid dianhydride and 
p-chlorophenol, in critical molar portions, are reacted together in oleum 
having boric acid dissolved therein. 
DETAILED DESCRIPTION OF THE INVENTION 
The bis-quinizarin compounds are prepared by reacting p-chlorophenol with 
an aromatic tetracarboxylic acid dianhydride having the structure: 
##STR6## 
where R has the structure: 
##STR7## 
where X is 
##STR8## 
or a bond. Examples of suitable compounds include 
3,3',4,4'-benzophenonetetracarboxylic acid dianhydride 
(BTDA),3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 
2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 
bis(3,4-dicarbyxyphenyl)ether dianhydride, 
naphthalene-2,3,6,7-tetracarboxylic acid dianhydride, 
bis(3,4-dicarboxyphenyl)methane dianhydride, 
bis(3,4-dicarboxyphenyl)sulfone dianhydride, and the like. Such compounds 
are known and reported in the art. 
The p-chlorophenol and the dianhydride, in molar portions subsequently 
described, together with boric acid are heated in oleum to a temperature 
of at least 175.degree. C. to form the desired bis-quinarizin compound. 
Stoichiometric considerations require that 2 moles of the p-chlorophenol 
react with 1 mole of the dianhydride. It has been observed that the 
formation of undesired by-products is minimized by employing an excess of 
the dianhydride. It is preferred to employ only 1.1 to 1.9 and more 
especially 1.4-1.8 molar portions of the p-chlorophenol for each molar 
portion of the dianhydride. Boric acid plays a role in the reaction and 
should be employed in an amount at least molarly equivalent to the 
p-chlorophenol. 
Oleum is the reaction solvent employed and should contain at least about 10 
weight % of SO.sub.3. Larger excesses of SO.sub.3 can be employed but are 
not required. When commercial grade 98% concentrated sulfuric acid is 
employed as the reaction solvent, additional incompletely identified 
co-products are formed which are difficult to separate from the desired 
bis-quinizarin product. Although the quantity of oleum employed is not 
critical, it is preferred to employ at least 2 and preferably at least 4 
parts by weight of oleum for each part of combined weight of 
p-chlorophenol and dianhydride. 
The solution of p-chlorophenol, dianhydride, boric acid and oleum is heated 
to a temperature of at least 175.degree. C. while providing stirring. The 
reaction mixture is held at this temperature for a sufficient period of 
time to complete the reaction. Eight to ten hours is usually sufficient. 
At the conclusion of the reaction, after cooling, the entire reaction 
mixture is poured into a large volume of water. The bis-quinizarin product 
is insoluble in water at pH 2 or less and can be boiled to aid in removing 
the excess dianhydride charged to the reaction mixture. Several washings 
should be made to obtain a product of high purity. In subsequent washings, 
a mineral acid such as sulfuric or hydrochloric should be added if 
required to maintain the pH below 2. Where a product of maximum purity is 
desired, the washed bis-quinizarin can be dissolved in dilute caustic 
solution and filtered. Acidification of the filtrate precipitates the 
bis-quinizarin.

The following example is set forth to illustrate the invention to those 
skilled in the art. 
EXAMPLE 1 
Part A 
A three-necked flask, equipped with a mechanical stirrer, a thermometer, 
and a nitrogen inlet, was charged with approximately 325 grams of 10% 
oleum. There then was added to the reactor, in sequence over a period of 
approximately 5 minutes, 48.7 grams (0.379 mol) of p-chlorophenol, 70.7 
grams (0.219 mol) of 3,3'4,4'-benzophenonecarboxylic acid (BTDA) and 33.6 
grams (0.54 mol) of boric acid. At the conclusion of these additions, the 
temperature in the flask had increased to 78.degree. C. The reaction 
mixture was heated to 190.degree. C. over a period of 1.5 hours and then 
was maintained at a temperature of 188.degree.-194.degree. C. for an 
additional period of 9.5 hours. The reaction mixture was cooled to 
substantially ambient temperature, poured into 1300 ml of water, stirred 
for 15 minutes, and filtered. The precipitate was a very dark red color. 
The product was resuspended in an additional 1300 ml of water with 
stirring, heated to the boiling point for two hours, and again filtered. 
The product was again slurried in 1300 ml of water and boiled for an 
additional 30-minute period. The recovered dark red solid then was 
dissolved in 500 ml of 10% aqueous KOH to provide a solution which had a 
deep blue color. The alkaline solution was acidified with 100 ml of 
commercial grade concentrated hydrochloric acid to reprecipitate the 
product as a dark red solid. The product was filtered and washed with 
deionized water until the pH of the filtrate reached a value of 2.0. It 
was noted that as the pH approached 2.0, a portion of a solid material 
appeared to dissolve. The product was dried in a vacuum oven at 
100.degree. C. for 24 hours to obtain a yield of 77.8 grams (81% of 
theory) of the desired, 6,6'-carbonyl bis-quinizarin (CBQ). The product 
melted over a range of 272.degree.-278.degree. C. 
An IR spectrum of the product showed no anhydride absorptions. A small 
aliquot of the product was dissolved in N-methyl-2-pyrrolidone (NMP) and 
separated into components by liquid chromatography employing a 
microporasil column. The product contained one main component and only 
trace amounts of three other components which were not identified. 
Part B 
Several attempts were made to prepare CBQ from the same reactants employed 
in Part A. The process conditions were essentially the same except that 
commercial grade concentrated sulfuric acid (98%) was employed in lieu of 
the oleum of Part A. The IR spectrum of the product obtained showed 
absorption bonds indicative of the presence of anhydride groups. A 
solution of the product in NMP was separated by liquid chromatography 
(using a microporasil column) into two major components, which were 
present in approximately equal amounts, and two minor components. 
The bis-quinizarin compounds of the invention have intense colors and very 
limited solubility in hydrocarbon solvents. For these reasons, they have 
utility as organic pigments in surface coating compositions (paints, 
lacquers, and the like), resin compositions, printing inks, and the like. 
They can be employed as intermediates in the manufacture of dyes, 
antioxidants, and the like. 
To prepare an attractive red colored polystyrene composition, one part of 
the CBQ particles of Example 1, Part A, can be dry blended with one 
thousand parts of a finely ground colorless polystyrene crystal containing 
about 0.2% stearic acid as a lubricant. The blending can be carried out in 
a conventional tumbling type blender. The mixture can be extruded at 
temperatures of about 450.degree.-500.degree. F. to form strands which 
then can be cut into pellets of a size suitable for use in an injection 
molding machine. Test molding specimens measuring 3".times.7".times.1/4" 
have an attractive red color. 
The bis-quinizarin compounds contain structural groupings very similar to 
those present in quinizarin. They may be viewed as being made from two 
mols of quinizarin joined together through the X groups of the first 
formula set forth above. For this reason, they undergo virtually all of 
the known quinizarin reactions and produce useful and attractive dye 
stuffs. For a general review of the type of reactions possible, see 
Chapter XXIX of the text The Chemistry of Synthetic Dyes by K. 
Venkataraman, Volume II, Academic Press of New York, 1952, Library of 
Congress Catalog Card Number 52-5201. By way of specific example, when an 
aqueous solution of CBQ, sodium sulfite and copper oxide is boiled, the 
sodium salt of the bis-2-sulfonic acid is obtained in virtually a 
quantitative yield. 
By employing conditions similar to those disclosed in British Pat. No. 
419,954, it is possible to prepare an attractive dye by first condensing 
four mols of p-toluidine with CBQ, then oxidizing the vat mixture, and 
finally sulfonating the product. The structure of the sodium salt is 
believed to be: 
##STR9## 
By an identical series of reactions, additional attractive dyes are 
prepared by substituting p-aminodiphenyl or 
1,2,3,4-tetrahydro-2-naphthylamine for the p-toluidine.