Heterocyclic polynuclear pigments and process for preparing same

New compounds are disclosed having the general formula: ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 may be the same or different and are selected from the class consisting of H, Cl and OCH.sub.3. They are useful as pigments. They are prepared by reacting a substituted or unsubstituted 1-aza-2-hydroxybenzanthrone with 2,3-dichloro-1,4-naphthoquinone, in the presence of pyridine, at a temperature between 80.degree. and about 120.degree. C.

This invention relates to a new class of heterocyclic polynuclear 
compounds, and to a method of preparing same. 
This class of compounds is represented by the following general formula; 
##STR2## 
wherein R.sub.1, R.sub.2, R.sub.3 may be the same or different and are 
selected from H, Cl and OHC.sub.3. 
When R.sub.1, R.sub.2, R.sub.3 = H, the compound may be defined as 
5,9,14-trioxo, 15-oxa, 16-aza-anthra[b,c]-benzo[h]-fluorene. 
These compounds have a color varying from red to yellow depending upon the 
substituents R.sub.1, R.sub.2, R.sub.3. By virtue of their excellent 
stability, they are particularly useful as pigments. 
A further feature of the present invention resides in the fact that the 
compounds in question are easily prepared by condensing, in the presence 
of pyridine, 1-aza-2-hydroxybenzanthrone (II), or its substituted 
derivatives, with 2,3-dichloro-1,4-naphthoquinone (III) according to the 
following reaction: 
##STR3## 
where R.sub.1, R.sub.2, R.sub.3 have the meanings specified hereinbefore. 
The substituted derivatives of 1-aza-2-hydroxybenzathrone (II) readily 
employable according to this invention include, for example, the 
following: 
1-aza-2-hydroxy-8-chlorobenzanthrone; 
1-aza-2-hydroxy-9,10-dichlorobenzanthrone; 
1-aza-2-hydroxy-8-methoxybenzanthrone. 
The starting materials necessary to practice the present invention are 
readily available, because 2,3-dichloro-1,4-naphthoquinone (III) is a 
commercial product existing on the market while 
1-aza-2-hydroxybenzanthrone (II) is easily obtained from 
1-amino-anthraquinone according to the method described in Italian Pat. 
No. 955,384 and in Italian Patent Application No. 26722 A/73corresponding 
to Belgian Pat. No. 817,725. 
Compound (II) is obtained according to the following process: 
Anthraquinone-1-diazonium sulphates (either simple or substituted by 
R.sub.1, R.sub.2 and R.sub.3 defined as above) are reacted with 
1,1-dichloro-ethylene in the presence of cuprous salts, and especially 
cuprous halides such as the chloride, bromide and iodide, and of alcohols 
(e.g., CH.sub.3 OH), thus obtaining the esters of anthraquinone-1-acetic 
acid (Italian Pat. No. 955,384). These esters, by treatment with ammonia 
in a hydroxylated solvent (CH.sub.3 OH; H.sub.2 O), in the presence of 
strong bases and/or reducing agents (e.g., zinc powder), are converted 
into intermediate compound (II) (Belgian Pat. No. 817,725). 
With regard to derivatives of 1-aza-2-hydroxy-benzanthrone, i.e., where 
R.sub.1, R.sub.2 and/or R.sub.3 are different from H, although these have 
not been exemplified in the above-cited patents and patent application, 
nevertheless they can be readily prepared starting from the corresponding 
substituted 1-amino-anthraquinones by proceeding in an otherwise similar 
way. 
Thus, it is an object of the present invention to provide a new class of 
compounds having useful applications in the pigments field. 
This and still other objects, which will become more clearly apparent to 
those skilled in the art from the following description, are achieved by a 
process for preparing compounds having formula (I), characterized in that 
1-aza-2-hydroxybenzanthrone (II) is reacted with 
2,3-dichloro-1,4-naphthoquinone (III) in the presence of pyridine at a 
temperature ranging from 80.degree. to about 120.degree. C. 
The molar ratio between the two reagents is essentially stoichiometric, but 
it is preferable to employ a slight excess (5-15%) of the 
2,3-dichloro-1,4-naphthoquinone. 
Depending on the particular temperature employed, the reaction time may 
range from 2 to about 5 hours. 
Pyridine is used in an amount sufficient to insure that the reaction 
mixture can be easily stirred. In practice, at least 10 parts of pyridine 
per part of 1-aza-2-hydroxybenzanthrone compound are employed. Parts are 
intended by weight. 
In carrying out the reaction it is advantageous to utilize pyridine 
because, besides being a good solvent for the reagents, this is also 
capable of neutralizing the hydrochloric acid evolved during the reaction. 
According to the particularly useful embodiment of this invention, for 
example, it is practiced as follows: 1-aza-2-hydroxybenzanthrone or its 
substituted derivatives and 2,3-dichloro-1,4-naphthoquinone are heated 
under stirring in the presence of pyridine to a temperature ranging from 
80.degree. to 120.degree. C for a reaction time of 2 to 5 hours. At the 
conclusion of the reaction, the reaction mixture containing the 
condensation product in suspension is filtered, without prior cooling. The 
filtered condensation product is washed at first with pyridine, or with 
dimethylformamide, in which it is practically insoluble, then with water 
and at least (optionally) with acetone. 
Due to the mild operating conditions, the process is particularly 
advantageous. Additional advantages consist in that the new pigments 
obtained according to the present invention exhibit excellent properties, 
such as stability to sunlight, to elevated temperatures, and to solvents, 
and in consequence, they may be used for the mass coloring of plastic 
materials such as polystyrene, polyvinyl chloride, polyamides, polyesters, 
polyacrylonitrile, cellulose acetates, etc. 
Furthermore they may be used in the preparation of paints and printing 
inks. 
The following examples are given to still better illustrate the invention, 
without however limiting same. Example 2 includes also the preparation of 
starting intermediates according to techniques cited above. Furthermore, 
Example 5 illustrates a typical application of the novel compounds of this 
invention.

EXAMPLE 1 
A mixture consisting of 20 g of 1-aza-2-hydroxybenzanthrone, 20 g of 
2,3-dichloro-1,4-naphthoquinone, and 320 cc of pyridine was heated at 
reflux and under stirring for 2 hours. It was then cooled down to room 
temperature, whereupon the solid product was filtered, washed with 
dimethylformamide, then with water and finally with acetone. 
After drying, there was obtained 27 g of an orange pigment having the 
following structural formula: 
##STR4## 
Elemental analysis, the IR-spectrum and the mass spectrum all corresponded 
to the above structural formula of the compound thus obtained. 
EXAMPLE 2 
1. Preparation of 5-chloro-anthraquinone-1-methyl acetate 
22 g of sodium nitrite were added, under stirring, in 15 minutes, to 300 cc 
of concentrated sulphuric acid. After obtaining a homogeneous solution, 55 
g of 1-amino-5-chloroanthraquinone were added in 1 hour, keeping the 
temperature at 30.degree. C. The mixture then was heated to 50.degree. C 
for about 20 minutes, then it was cooled to 30.degree. C, and the solution 
was gradually poured onto 600 g of ice. 
The precipitated diazonium salt, after filtering and washing with methanol, 
was added to a mixture made up of 500 cc of methanol and 200 cc of 
1,1-dichloro-ethylene. The mixture was stirred at 30.degree. C, 5 g of 
hydrochloric acid in 20 cc of methanol were added, and then cuprous 
chloride in portions of 50 mg each, until nitrogen began to evolve. (Total 
amount of added cuprous chloride: about 0.25 g.) 
The reaction was exothermic and the temperature was kept at 30.degree.- 
35.degree. C by means of cooling. Nitrogen evolution stopped after about 
30 minutes and a precipitate of 5-chloroanthraquinone-1-methylacetate 
began to form. This was followed by heating at reflux for about 30 
minutes, whereupon both 1,1-dichloro-ethylene and methanol distilled, 
until the vapors reached 65.degree. C. After cooling to 20.degree. C, the 
precipitate was filtered and washed with methanol to neutrality. 60 g of 
5-chloroanthraquinone-1-methylacetate were thus obtained after drying. 
2. Preparation of 1-aza-2-hydroxy-8-chlorobenzanthrone 
60 g of ammonia were absorbed in 300 cc of methanol, cooled down to 
-10.degree. C, then 30 g of 5-chloro-anthraquinone-1-methylacetate and 1 g 
of zinc powder were added thereto. The mixture was kept under stirring for 
about 5 hours at room temperature and at a pressure of 1.4 kg/cm.sup.2. It 
was heated to 60.degree. C to remove ammonia, diluted with 2 l of 
methanol, rendered alkaline with 25 g of 50% NaOH, heated to 60.degree. C 
for about 20 minutes, and filtered on kieselguhr. The filtered solution 
was diluted with 1 l of water and acidified with concentrated hydrochloric 
acid. 
The resulting yellow-colored precipitate was filtered and then washed with 
water to neutrality. 
After drying, there was obtained 23.4 g of 
1-aza-2-hydroxy-8-chlorobenzanthrone having the structural formula: 
##STR5## 
3. Preparation of the pigment according to this invention 
A mixture consisting of 20 g of 1-aza-2-hydroxy-8-chlorobenzanthrone 
obtained as described above, 17.6 g of 2,3-dichloro-1,4-naphthoquinone, 
and 320 cc of pyridine was heated at reflux and under stirring for about 3 
hours. At the conclusion of the reaction, it was hot-filtered and the 
solid product obtained was washed successively with pyridine, hot water, 
dimethylformamide and, finally, acetone. 
After drying, there was obtained 26.4 g of an orange pigment having the 
following structural formula: 
##STR6## 
This corresponds to formula (I) where R.sub.1 = R.sub.2 = H and R.sub.3 = 
Cl. 
Elemental analysis, the IR-spectrum and the mass spectrum of the products 
obtained as described above corresponded to the formulas given. 
EXAMPLE 3 
Operating according to the procedure described above in Example 2 but using 
1-amino-6,7-dichloroanthraquinone as starting reactant, 
1-aza-2-hydroxy-9,10-dichlorobenzanthrone was obtained, an orange powder 
having the following structural formula: 
##STR7## 
A mixture consisting of 22.4 g of 
1-aza-2-hydroxy-9,10-dichlorobenzanthrone, 17.6 g of 
2,3-dichloro-1,4-naphthoquinone, and 600 cc of pyridine was heated at 
reflux for about 3 hours. On completion of the reaction, it was 
hot-filtered and the resulting solid product was washed successively with 
pyridine, hot water, dimethylformamide and, finally, acetone. 
After drying, there was obtained 24.8 g of an orange pigment having the 
following structural formula: 
##STR8## 
wherein R.sub.1, R.sub.2 of formula (I) = Cl and R.sub.3 = H. 
Elemental analysis, the IR-spectrum and the mass spectrum of the products 
so obtained corresponded to the formulas given. 
EXAMPLE 4 
Operating according to the procedure described above in Example 2 but 
employing 1-amino-5-methoxyanthraquinone as starting reactant, 
1-aza-2-hydroxy-8-methoxybenzanthrone was obtained, a yellow-colored 
powder having the following structural formula: 
##STR9## 
A mixture consisting of 25 g of 1-aza-2-hydroxy-8-methoxybenzanthrone, 23 g 
of 2,3-dichloro-1,4-naphthoquinone, and 400 cc of pyridine was heated at 
reflux for about 3 hours. At the conclusion of the reaction it was cooled 
down to room temperature, and the solid product filtered, washed with 
pyridine, hot water, dimethylformamide and, finally, acetone. 
After drying, there was obtained 25 g of a red pigment having the following 
structural formula: 
##STR10## 
wherein R.sub.3 of formula (I) = OCH.sub.3 and R.sub.1 = R.sub.2 = H. 
Elemental analysis, the IR-spectrum and the mass spectrum of the products 
so obtained corresponded to the formulas given. 
EXAMPLE 5 
Dyeing of plastic materials and paint compositions with the pigments 
obtained as described in the preceding examples was readily carried out by 
incorporating same therein by means of suitable well-known mixing, 
blending and kneading equipment, such as the three-cylinder refiner, the 
disk mill, etc., according to per se conventional techniques. 
In applications with polyvinyl chloride for making plasticized shaped 
articles, the PVC resin in powder form was hot-mixed (70.degree. C) in a 
rotating arm mixer with the necessary and conventional amounts of 
plasticizers, stabilizers, fillers and the pigment. 
Operating according to techniques and recipes already per se known, the 
following materials were treated at 180.degree. C in a three-cylinder 
refiner until thorough dispersion of the pigment was effected: 
100 g of polyvinyl chloride; 
1.5 g of a Ba or Cd complex salt of a higher fatty acid (stearic acid) 
having a complex and antioxidizing action; 
3 g of epoxidized soybean oil; 
0.5 g of lubricant (glycerides from C.sub.16 to C.sub.36); 
2 g of TiO.sub.2 ; and 
1 g of pigment prepared according to Example 1. 
A plastic sheet having an orange shade and exhibiting excellent fastness to 
sunlight and to solvents as well as excellent thermostability was thus 
obtained. 
The pigment prepared according to Example 1, when incorporated in 
polystyrene, imparts a bright yellow dyeing thereto. 
Analogous results were obtained by employing the pigments produced 
according to Examples 2, 3 and 4 in an otherwise similar manner.