FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
PROVISIONAL / COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION :
AN IMPROVED PROCESS FOR PREPARING BIS (2-BENZOXAZOLYL) STILBENES.
2. APPLICANT
(a) NAME : SUDARSHAN CHEMICAL INDUSTRIES LTD.
(b) NATIONALITY: An Indian Company registered under the provisions of
the Companies Act, 1956.
(c) ADDRESS : 162, Wellesley Road,
PUNE- 411001, Maharashtra State, India.
3. PREAMBLE TO THE DESCRIPTION

PROVISIONAL
The following specification invention.

describes the

COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

4. DESCRIPTION (Description starts from page 2)

5. CLAIMS:

Given on a separate sheet

6. DATE AND SIGNATURE: Given at the end of last page of specification.
7. ABSTRACT OF THE INVENTION: Given on a separate sheet
1

Technical Field:
The present invention relates to a preparation of bis (2-benzoxazolyl) stilbenes. More particularly, present invention relates to an improved process for the preparation of 4,4'-bis(2-benzoxazolyl)stilbene compounds by the reaction of 4,4'-stilbenedicarboxylic acid dihalide with 2-aminophenol compounds in the presence of catalyst and organic polar solvent.
Background and Prior Art:
Bis(2-benzoxazolyl) stilbene derivatives are useful as fluorescent brightening agents and light stabilizers for polyolefin and polyester fibers and shaped articles.
In prior art processes, the preparation of symmetrical bis (2-benzoxazolyl) stilbene derivatives follows two different approaches.
British Patent 1,072,918; Japanese Patent 66-018,838; and U.S. Pat. Nos. 3,546,217; 3,476,747; and 3,819,615 has described processes wherein, both benzoxazole rings are formed prior to the formation of the stilbene nucleus to obtain symmetrical compounds.
Another approach provides symmetrical compounds which involve the formation of the stilbene nucleus prior to the formation of both benzoxazole rings. Such processes are disclosed in Japanese Patents 68-000-811; 66-008,573; 68-028,017; 68-030,193; 70-000,771, French Patent 1,397,727; and U.S. Pat. Nos. 3,412,089; 3,575,996; 3,366,575; 3,860,584; 3,585,208.
The preparation of bis (2-benzoxazolyl) stilbenes is disclosed in U.S. Patent. No. 3,412,089, wherein, dialkyl-4,4'-stilbenedicarboxylate and substituted o-aminophenol are reacted in polyphosphoric acid at 200.degree.-230.degree. to obtain product.
In this process polyphosphoric acid is used as dehydrating agent as well as solvent requiring the subsequent use of a basic material.
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U.S. Patent No. 4,921,964 disclosed the preparation of bis(2-benzoxazolyl)stilbene compounds by the reaction of dialkyl 4,4'-stilbenedicarboxylate with various 2-aminophenol compounds in the presence of certain solvents that boils above 200°, preferably naphthalene derivatives and tin /titanium compound as catalysts.
4,4'-stilbenedicarboxylic acid has been used as a starting material in the process disclosed in U.S. Pat. No. 5,332,828, wherein, 4,4'-stilbenedicarboxylic acid is reacted with 2-aminophenol compounds in the presence of a tin or titanium catalyst and certain high boiling solvents at 200-300°C.
Another process for producing bis(2-benzoxazolyl)stilbene is described in Chinese patent CN 1517348, that involves cyclcondensation of dihydrochloride derivative of dialkyl 4,4'-stilbenedicarboxylate with 2-aminophenols in organic acid or lower alcohols.
Thus any method for producing bis(2-benzoxazolyl)stilbene product with high purity which is safer, easier to handle and overcomes the various disadvantages of the prior art procedures, would be very desirable.
Description of the Present Invention:
The present invention relates to a process for producing bis(2-benzoxazolyl)stilbenes that comprises preparing mixture of 4,4'-stilbenedicarboxylic acid dihalide with 2-aminophenol compounds, and heating the mixture in the presence of a catalyst in organic polar solvent to provide bis(2-benzoxazolyl)stilbene product with an improved colour specification.
The bis(2-benzoxazolyl)stilbenes of formula I where R is H or CH3 prepared by the process of the present invention by reacting 4,4'-stilbenedicarboxylic acid dihalide of formula II where X is CI or Br with 2-aminophenol compounds of formula III where R is
3

H or CH3 in presence of catalyst and polar organic solvent at temperature ranging from about 80 deg C to 170 deg C as shown below.

(I)
According to the present invention, bis(2-benzoxazolyl)stilbenes is produced by reacting the reactants described above at 80°C-170°C in polar organic solvent medium. The suitable organic polar solvents used in present invention are substantially unreactive toward reactants, products. The preferred organic polar solvent is glacial acetic acid.
The cone. Sulphuric acid can be used in present invention and are well known esterification, polyesterification, alcoholysis, and acidolysis catalysts. In present invention, the preferred catalyst is concentrated sulphuric acid.
The process typically is carried out over a temperature range of about 80 deg C to 170 deg C, preferably 100 deg C- 150 deg C. Pressure normally is not an important process condition and the process therefore normally is performed at ambient pressure or
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moderately elevated pressure generated in a sealed reactor if used, i.e., autogenously pressures
The reaction is conducted in a substantially oxygen-free atmosphere. For example, an inert gas such as nitrogen or argon can be continuously passed through the reaction zone during the condensation.
The 4,4'-bis(2-benzoxazolyl)stilbene compounds in the present invention obtained are pale yellow or yellow crystals having strong yellow fluorescence in UV light and yield according to present invention is un optimized.
Example:
Into a four neck round bottom flask equipped with a nitrogen inlet and outlet, mechanical stirrer and a condenser were charged 6-10 part glacial acetic acid per gm of formula II( X=C1, Br), 0.0655 moles of compound II( X=C1, Br), 2-2.2 mole equivalent of o-aminophenol( R=H, Me) and 0.2-0.4 mole equivalent Cone. Sulphuric acid with nitrogen protection. The mixture was stirred at room temperature under nitrogen purging for 15-45 minutes. The mixture was heated slowly to 80 deg C -130 deg C and maintained at 120-130 deg C for period of 10-20 hours. The progress of reaction was monitored by Thin Layer Chromatography(TLC). The resultant yellowish suspension was cooled to 30 deg C, -10°C filtered through suction and washed with water(4x.50ml). The crude product thus obtained was treated with 5% Sodium hydroxide(l-2mole equivalent) at 80°C under stirring for 1-2 hours, filtered at 40°C, washed with water to neutral pH get pure product. The product bis-(2-benzoxazolyl) stilbene thus obtained was dried under reduced pressure at 70-90°C till constant weight .Yield 60-65 %(unoptimized). It was analyzed by High pressure liquid chromatography (HPLC) for its purity. The product obtained was characterized by elementary analysis, IR and UV.
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Advantages of the Present Invention:
1. The present invention does not require high reaction temperature (above 200°C) and is performed at lower temperature than conventional methods.
2. The present invention provides improved color with high purity.
3. Solvents used in present invention are low cost and can be easily recycled where as in
prior art processes has used high boiling solvents which either difficult to recycle or can
not be recycled.
6

We Claim:
1. An improved process for preparing bis(2-benzoxazolyl)stilbenes of formula I wherein R is H or CH3 comprising of reacting 4,4'-stilbenedicarboxylic acid dihalide of formula II wherein X is CI or Br with 2-aminophenol compounds of formula III in the presence of catalyst and polar organic solvent at temperature ranging from about 80 deg C to 170 deg C as shown below.

(I)
2. An improved process for preparing bis(2-benzoxazolyl)stilbenes of formula(I) as
claimed in claim 1 wherein the catalyst is cone. Sulphuric acid.
3. A process as claimed in claim 1 wherein the polar organic solvent is glacial acetic acid.
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4. A process as claimed in claim 1 wherein 2-amino phenol compound is used in 2-2.2 mole equivalent.
5. A process as claimed in claim 1 wherein catalyst is used in 0.2-0.4 mole equivalent.
6. A process as claimed in claim 1 substantially as herein described with reference to
the example and specification.
Dated this 23rd day of June, 2007.


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Abstract
(I)
The present invention relates to a improved process for preparing bis(2-benzoxazolyl)stilbenes of formula I comprising of reacting 4,4'-stilbenedicarboxylic acid dihalide of formula II with 2-aminophenol compounds of formula III in the presence of catalyst and polar organic solvent at temperature ranging from about 80 deg C to 170 deg C as shown below.