Title of Invention	"A PROCESS FOR THE PREPARATION OF NOVEL DISPERSE DYES FROM NAPHTHO [1,8-CD] DITHIOLE"
Abstract	A process for the preparation of novel disperse dyes having general formula II from naphtho [1,8-cd] dithiole by treating a substituted aromatic amine with a diazotising agent in an acidic medium at a temperature in the range of -20° to 30°C, coupling with an organic acid solution of naphtha [1,8-cd] dithiole at a temperature ranging from -20° to 30°C, maintaining the pH of the above said reaction mixture ranging between 4 to 5 by adding a buffer selected from alkali metal acetate under constant stirring for a period ranging from 2-6 hrs., quenching the reaction with water and separating and recovering disperse dye by conventional methods.

Title of Invention

"A PROCESS FOR THE PREPARATION OF NOVEL DISPERSE DYES FROM NAPHTHO [1,8-CD] DITHIOLE"

Abstract

A process for the preparation of novel disperse dyes having general formula II from naphtho [1,8-cd] dithiole by treating a substituted aromatic amine with a diazotising agent in an acidic medium at a temperature in the range of -20° to 30°C, coupling with an organic acid solution of naphtha [1,8-cd] dithiole at a temperature ranging from -20° to 30°C, maintaining the pH of the above said reaction mixture ranging between 4 to 5 by adding a buffer selected from alkali metal acetate under constant stirring for a period ranging from 2-6 hrs., quenching the reaction with water and separating and recovering disperse dye by conventional methods.

Full Text	This invention relates to a process for the preparation of novel disperse dyes from Naptho [1,8-cd] dithiole. More particularly, the present invention relates to a process for the preparation of novel disperse monoazo dyes from Naptho [1,8-cd] dhhiole as the coupling component in excellent yields. The dyeing characteristics of the monoazo disperse dyes derived from it have also been evaluated. Substituted "naphtho [1,8-cd] dithiole has been used as an antiviral agent (Jpn. Kokai Tokkyo Koho Jp. 0803,039, CA 124, 220499q, 1996). It also has been used for the protection of aldehydes and ketones (Compt. Rend, 152, 92-94, 1911. Fr). These protected aldehydes and ketones can be easily deprotected to regenerate them in high yields without the use of either the unpleasant smelling alkylthiols, or heavy metals or strong acids. Recently H has been found that naphtho [1,8-cd] dithiole has the capability to form redox active self-assembled monolayer on gold (Langmuir 13, 866-869, 1997) Like aromatic sulfides in general, naphthof 1,8-cd] dithiole is a bright red crystalline substance and possesses an anomalously deep color for such a simply constructed compound [Ref: (1) H.S. Desai and B.D. Tilak, J.Sci fad. Res. (India) 19B, 390 1960); Compt. Rend 152 92-94 (Fr) (1911); W.B. Price and S. Smiles, JCS 2372, • (1928)]. Attempts to explain this effect theoretically by means of the dipole moment method or UV and IR spectroscopy [Ref. H.S. Desai and B.D. Tilak, J.Sci Ind. Res. (India) 19B, 390 (I960)] led to the conclusion that a necessary condition for the deep color of this compound is the coplanarity of the S-S group and the 7t electron system of the naphthalene. A consequence of this could be 3p-3d overlap of the unshared electrons of the adjacent sulfur atoms or interaction of the 3p electrons of one sulphur atom with the 3d orbital of the adjacent sulfur atom. Data from the quantum chemical character also indicate strong delocalization of the 3p electrons of the S-S group and the formation of a general n electron system. Disperse dyes are colorants with low water solubility which in then* disperse colloidal form are suitable for dyeing and printing hydrophobic fibres and fabrics. Since 1950, the production of disperse dyes has increased sharply, closely following the growth i' -. in the worldwide production of synthetic fibres especially polyester. Furthermore, new dyeing processes necessitated the development of special disperse dyes. When the dye is applied from aqueous medium it is absorbed from the molecularly disposed aqueous solution onto the fibre surface and diffuses into the interior of the fibre. Differences in geometry and polarity of the dyes can have a marked effect on the absorption characteristics of dyes Although a variety of methods are known to be used for the preparation of Naptho[l,8-cd] dithiole, there is no study of disperse dyes derived from Naptho[l,8-cd]dithiole and their dyeing characteristics on fiber. This may be attributed to t the complex preparatory methods that are reported for naptho[l,8-cd]dithiole yielding the latter in very poor yields. The object of the present invention is to provide a process for the preparation of * new disperse dyes from Naptho[l,8-cd]dithiole having good light and sublimation fastness properties and their study as potential disperse dyes for polyester fiber (Formula Removed) FORMULA I FORMULA II Accordingly, the present invention provides a process for the preparation of novel disperse dyes having general formula II from naphtho [1,8-cd] dithiole of formula I wherein R is a substituted cyano phenyl. cyano nitro phenyl, alkoxy phenyl, alkyl nitro phenyl, helo phenyl or halo nitro phenyl which comprises. treating a substituted aromatic amine with a diazotising agent in an acidic medium at a temperature in the range of-20° to 30°C, coupling with an organic acid solution of naphtha [1,8-cd] dithiole at a temperature ranging from -20° to 30°C, maintaining the pH of the above said reaction mixture ranging between 4 to 5 by adding a buffer under constant stirring for a period ranging from 2-6 hrs., quenching the reaction with water and separating the compound by conventional methods like extraction, distillation and filtration to obtain the desired product. In one of the embodiment of the present invention, the substituted aromatic amine used is selected from the group consisting of substituted cyano phenyl amine such as 4-cyano phenyl amine, substituted cyano nitro phenyl amine such as 2-cyano-4-nitro phenyl amine, substituted alkoxy nitro phenyl such as 4-methoxy-2 nitro phenyl, substituted helo phenyl amine selected from 3-chloro-4-flouro phenyl amine, 2- i flour.0 phenyl amine and 2,4 dichloro phenyl amine, substituted alkyl nitro phenyl amine such 4 methyl-3 nitro phenyl amine and substituted halo nitro amine such as 4-chloro-2 nitro phenyl amine. In yet another embodiment, the diazotising agent used is a mineral acid solution of alkali metal nitrite selected from the group consisting of sodium nitrite, potassium nitrite and lithium nitrite preferably sodium nitrite. In yet another embodiment, the mineral acid used is selected from sulphuric acid and hydrochloric acid preferably sulphuric acid. In yet another embodiment, the organic acid used is selected from acetic acid and propionic acid preferably acetic acid. In still another embodiment, the buffer used is an alkali metal acetate selected from sodium acetate and potassium acetate, preferably sodium acetate. The process of the present invention is described with examples herein below, which are illustrative only and should not be construed to limit the scope of the present invention in any manner. EXAMPLE - 1 This example illustrates preparation of 2-(2-cyano-4-nitrophenyIazo>-naphtho[l,8-cd]dithioIe.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round-bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-cyano-4-nhro aniline (1.63 g, 0.01 mol) hi 15 ml glacial acetic acid at 0°- 5°C. -After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. * Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed; the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye: 75% (m.p. 265°-268°C). EXAMPLE-2 This example illustrates preparation of 2-(2-nitro-4-methoxyphenylazo)-naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round-bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-nitro-4-methoxy aniline (1.68 g, 0.01 mol) in 15 ml glacial acetic acid at s 0°-5tfC. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 78% (m.p. 196°-198°C). EXAMPLE-3 This example illustrates preparation of 2-(2-chloro-4-flurophenyIazo naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-chloro-4-fluro aniline (1.63 g, 0.01 mol) hi 15 ml glacial acetic acid at 0°- i 5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 65% (m.p. 180°-182°C). EXAMPLE-4 This example illustrates preparation of 2-(2-flurophenylazo naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below S°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over IS min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for IS min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-fluroaniline (1.14 g, 0.01 mol) in IS ml glacial acetic acid at 0°-5°C. After addition, the mixture was stirred for IS min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to S°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 56% (m.p. 188°-190°C). EXAMPLE-5 This example illustrates preparation of 2-(2,4-dichloropbenylazo)- ••- naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled belbw 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2,4-dichloro aniline (1.62 g, 0.01 mol) in 15 ml glacial acetic acid at 0°- 5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°G for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 50% (m.p. 249°-251°C). EXAMPLE-6 This example illustrates preparation of 2-(2-nitro-4-methylphenyIazo) naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-nitro-4-methyl aniline (1.52 g, 0.01 mol) in 15 ml glacial acetic acid at 0°-5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 75% (m.p. 210°-212°C). EXAMPLE - 7 This example illustrates preparation of 2-(2-nitro-4-chlorophenyIazo) naphtho[l,8- i.'.. cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nhrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-nitro-4-chloro aniline (1.63 g, 0.01 mol) in 15 ml glacial acetic acid at 0°- i 5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] ditniole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 64% (m.p. 124°-127°C). EXAMPLE-8 This example illustrates preparation of 2-(4-cyanophenylazo)- »••, naphtho[l,8-cd]dfthio!e.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 4-cyanoaniline (1.06 g, 0.01 mol) in 15 ml glacial acetic acid at 0°-5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea. Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated hi 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 65% (m.p. 288°-290°C). The dyes prepared by the present invention maybe applied on polyester fibre by the process mentioned below. Dispersions of the dyes were prepared by milling 1 g of the dye, 1 g of Tamol NNO (dispersing agent) in water 25 ml in a glass tube containing steel rods for 48 h. The 1% dispersion of these dyes were used as stock solution for dyeing polyester fiber. The dye bath was set with 1% dispersion, 5% unisperse P ( a heat resistant leveling agent) and 1% acetic acid keeping the material liquor ratio 1 : 100. The material was entered at 60°C and the temperature raised to 130°C in 30 min. The dyeing was continued at 130°C for one more hour. After cooling the dyeings were taken out and given treatment with mixed solutions of sodium bisulfite 2% w/v and sodium hydroxide 4% w7v at 70°C for 15 min. Finally, the dyeings were rinsed well with water and dried at 60°C. t The dyed polyester fiber was tested for sublimation and light fastness properties and were found to be promising. In particular,the dyes imparting blue-green and violet shades (Examples 1&2) exhibited very good light and sublimation fastness properties. Overall, all the dyes showed very good sublimation fastness properties whereas, light fastness varied from moderate to very good. The fastness properties can be further improved by applying the dyes using thermo-fixation process instead of high temperature high pressure dyeing technique used in the present disclosure. The advantages of the present invention 1) This is the first disclosure of an efficient synthesis and study of dyeing characteristics of new disperse dyes derived from naphtho[l,8-cd] dithiole as a coupling component. 2) The products are pure enough and do not need further purification. 3) The dyes are:obtained in very good to excellent yields. 4) No sophisticated and moisture sensitive chemicals are used in the synthesis. 5) No side products are obtained in all the reactions. 6) The reactions are regioselective. 7) The reaction is very clean and work up involves minimum effort. 8) The dyes obtained from naptho [1,8-cd] dithiole as coupling component imparted bright blue to blue-green shades on polyester with very good light and sublimation fastness properties. 9) The azo dyes containing other substituents like nitro group can be used as a starting material for the synthesis of cationic dyes. 10) Naptho [1,8-cd] dithiole enters readily into the azo coupling reaction not only with such active diazonium ions as nitro and dinitro benzene diazonium salt but also with unsubstituted benzene diazonium ion. 11) The high polarisability of the chromophoric systems make them potential molecules for having non-linear optical (NLO) properties and as organic semi conductors. 12) The dyes may also find use as speciality colorants for plastics. We claim : 1. A process for the preparation of novel disperse dyes having general formula II from naphtho [1,8-cd] dithiole of formula I wherein R is a substituted cyano phenyl, cyano nitro phenyl, alkoxy phenyl, alkyl nitro phenyl, halo phenyl or halo nitro phenyl which comprises, treating a substituted aromatic amine with a diazotising agent in an acidic medium at a temperature in the range of -20° to 30°C, coupling with an organic acid solution of naphtha [1,8-cd] dithiole at a temperature ranging from -20° to 30°C, maintaining the pH of the above said reaction mixture ranging between 4 to 5 by adding a buffer under constant stirring for a period ranging from 2-6 hrs., quenching the reaction with water and separating the compound by conventional methods like extraction, distillation, (Formula Removed) FORMULA II 2. A process as claimed in claim 1, wherein the substituted aromatic amine used is selected from the group consisting of substituted cyano phenyl amine such as 4-cyano phenyl amine, substituted cyano nitro phenyl amine such as 2-cyano-4-nitro phenyl amine, substituted alkoxy nitro phenyl such as 4-methoxy-2 nitro phenyl, substituted helo phenyl amine selected from 3-chloro-4-flouro phenyl amine, 2-flouro phenyl amine and 2,4 dichloro phenyl amine, substituted alkyl nitro phenyl amine such 4 methyl-3 nitro phenyl amine and substituted halo nitro amine such as 4-chloro-2 nitro phenyl amine. A process as claimed in claims 1 & 2, wherein the diazotising agent used is a mineral acid solution of alkali metal nitrite selected from the group consisting of sodium nitrite, potassium nitrite and lithium nitrite preferably sodium nitrite. A process as calimed in claims 1-3, wherein the mineral acid used is selected from sulphuric acid and hydrochloric acid preferably sulphuric acid. A process as calimed in claims 1 to 4, wherein the organic acid used is selected from acetic acid and propionic acid preferably acetic acid. A process as claimed in claims 1-5, wherein the buffer used is an alkali metal acetate selected from sodium acetate and potassium acetate, preferably sodium acetate. A process for the preparation of novel disperse dyes from naphtho [1,8-cd] dithiole as fully described hereinbefore with reference to the examples and evening accompanying this .

Full Text

This invention relates to a process for the preparation of novel disperse dyes from Naptho [1,8-cd] dithiole. More particularly, the present invention relates to a process for the preparation of novel disperse monoazo dyes from Naptho [1,8-cd] dhhiole as the coupling component in excellent yields. The dyeing characteristics of the monoazo disperse dyes derived from it have also been evaluated.
Substituted "naphtho [1,8-cd] dithiole has been used as an antiviral agent (Jpn. Kokai Tokkyo Koho Jp. 0803,039, CA 124, 220499q, 1996). It also has been used for the protection of aldehydes and ketones (Compt. Rend, 152, 92-94, 1911. Fr). These protected aldehydes and ketones can be easily deprotected to regenerate them in high yields without the use of either the unpleasant smelling alkylthiols, or heavy metals or strong acids. Recently H has been found that naphtho [1,8-cd] dithiole has the capability to form redox active self-assembled monolayer on gold (Langmuir 13, 866-869, 1997)
Like aromatic sulfides in general, naphthof 1,8-cd] dithiole is a bright red
crystalline substance and possesses an anomalously deep color for such a simply constructed compound [Ref: (1) H.S. Desai and B.D. Tilak, J.Sci fad. Res. (India) 19B,
390 1960); Compt. Rend 152 92-94 (Fr) (1911); W.B. Price and S. Smiles, JCS 2372,
•
(1928)]. Attempts to explain this effect theoretically by means of the dipole moment method or UV and IR spectroscopy [Ref. H.S. Desai and B.D. Tilak, J.Sci Ind. Res. (India) 19B, 390 (I960)] led to the conclusion that a necessary condition for the deep color of this compound is the coplanarity of the S-S group and the 7t electron system of the naphthalene. A consequence of this could be 3p-3d overlap of the unshared electrons of the adjacent sulfur atoms or interaction of the 3p electrons of one sulphur atom with the 3d orbital of the adjacent sulfur atom. Data from the quantum chemical character also

indicate strong delocalization of the 3p electrons of the S-S group and the formation of a general n electron system.
Disperse dyes are colorants with low water solubility which in then* disperse colloidal form are suitable for dyeing and printing hydrophobic fibres and fabrics. Since 1950, the production of disperse dyes has increased sharply, closely following the growth
i' -.
in the worldwide production of synthetic fibres especially polyester. Furthermore, new dyeing processes necessitated the development of special disperse dyes. When the dye is applied from aqueous medium it is absorbed from the molecularly disposed aqueous solution onto the fibre surface and diffuses into the interior of the fibre. Differences in geometry and polarity of the dyes can have a marked effect on the absorption characteristics of dyes Although a variety of methods are known to be used for the preparation of Naptho[l,8-cd] dithiole, there is no study of disperse dyes derived from Naptho[l,8-cd]dithiole and their dyeing characteristics on fiber. This may be attributed to
t
the complex preparatory methods that are reported for naptho[l,8-cd]dithiole yielding the latter in very poor yields.
The object of the present invention is to provide a process for the preparation of
*
new disperse dyes from Naptho[l,8-cd]dithiole having good light and sublimation fastness properties and their study as potential disperse dyes for polyester fiber

(Formula Removed)
FORMULA I FORMULA II

Accordingly, the present invention provides a process for the preparation of novel disperse dyes having general formula II from naphtho [1,8-cd] dithiole of formula I wherein R is a substituted cyano phenyl. cyano nitro phenyl, alkoxy phenyl, alkyl nitro phenyl, helo phenyl or halo nitro phenyl which comprises. treating a substituted aromatic amine with a diazotising agent in an acidic medium at a temperature in the range of-20° to 30°C, coupling with an organic acid solution of naphtha [1,8-cd] dithiole at a temperature ranging from -20° to 30°C, maintaining the pH of the above said reaction mixture ranging between 4 to 5 by adding a buffer under constant stirring for a period ranging from 2-6 hrs., quenching the reaction with water and separating the compound by conventional methods like extraction, distillation and filtration to obtain the desired product.
In one of the embodiment of the present invention, the substituted aromatic amine used is selected from the group consisting of substituted cyano phenyl amine such as 4-cyano phenyl amine, substituted cyano nitro phenyl amine such as 2-cyano-4-nitro phenyl amine, substituted alkoxy nitro phenyl such as 4-methoxy-2 nitro phenyl, substituted helo phenyl amine selected from 3-chloro-4-flouro phenyl amine, 2-
i
flour.0 phenyl amine and 2,4 dichloro phenyl amine, substituted alkyl nitro phenyl amine such 4 methyl-3
nitro phenyl amine and substituted halo nitro amine such as 4-chloro-2 nitro phenyl amine.
In yet another embodiment, the diazotising agent used is a mineral acid solution of alkali metal nitrite
selected from the group consisting of sodium nitrite, potassium nitrite and lithium nitrite preferably
sodium nitrite.
In yet another embodiment, the mineral acid used is selected from sulphuric acid and hydrochloric acid
preferably sulphuric acid.
In yet another embodiment, the organic acid used is selected from acetic acid and propionic acid
preferably acetic acid.
In still another embodiment, the buffer used is an alkali metal acetate selected from sodium acetate and
potassium acetate, preferably sodium acetate.
The process of the present invention is described with examples herein below, which are illustrative only and should not be construed to limit the scope of the present invention in any manner.
EXAMPLE - 1
This example illustrates preparation of 2-(2-cyano-4-nitrophenyIazo>-naphtho[l,8-cd]dithioIe.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round-bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-cyano-4-nhro aniline (1.63 g, 0.01 mol) hi 15 ml glacial acetic acid at 0°-
5°C. -After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the
addition of urea.
*
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed; the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye: 75% (m.p. 265°-268°C).
EXAMPLE-2
This example illustrates preparation of 2-(2-nitro-4-methoxyphenylazo)-naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round-bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-nitro-4-methoxy aniline (1.68 g, 0.01 mol) in 15 ml glacial acetic acid at
s
0°-5tfC. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 78% (m.p. 196°-198°C).
EXAMPLE-3
This example illustrates preparation of 2-(2-chloro-4-flurophenyIazo naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-chloro-4-fluro aniline (1.63 g, 0.01 mol) hi 15 ml glacial acetic acid at 0°-
i
5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 65% (m.p. 180°-182°C).
EXAMPLE-4 This example illustrates preparation of 2-(2-flurophenylazo
naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below S°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over IS min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for IS min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-fluroaniline (1.14 g, 0.01 mol) in IS ml glacial acetic acid at 0°-5°C.
After addition, the mixture was stirred for IS min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to S°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 56% (m.p. 188°-190°C).
EXAMPLE-5 This example illustrates preparation of 2-(2,4-dichloropbenylazo)-
*••-
naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled belbw 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2,4-dichloro aniline (1.62 g, 0.01 mol) in 15 ml glacial acetic acid at 0°-
5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°G for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 50% (m.p. 249°-251°C).
EXAMPLE-6
This example illustrates preparation of 2-(2-nitro-4-methylphenyIazo) naphtho[l,8-cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-nitro-4-methyl aniline (1.52 g, 0.01 mol) in 15 ml glacial acetic acid at
*
0°-5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 75% (m.p. 210°-212°C).
EXAMPLE - 7 This example illustrates preparation of 2-(2-nitro-4-chlorophenyIazo) naphtho[l,8-
i.'..
cd]dithiole.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nhrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 2-nitro-4-chloro aniline (1.63 g, 0.01 mol) in 15 ml glacial acetic acid at 0°-
i
5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] ditniole (1.9 g 0.01 mole) was heated in 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 64% (m.p. 124°-127°C).
EXAMPLE-8
This example illustrates preparation of 2-(4-cyanophenylazo)-
»••,
naphtho[l,8-cd]dfthio!e.Concentrated sulfuric acid (4.4 ml, sp. gr. 1.83) was taken in a round bottomed flask. It was cooled below 5°C and sodium nitrite (0.73g, 0.011 mol) was added slowly over 15 min taking care that the temperature did not rise above 10°C and no brown fumes were evolved. After addition of sodium nitrite, the mixture was stirred at this temperature for 15 min. and then heated slowly to 70°C. The mixture, was kept at this temperature until all sodium nitrite dissolved to give a clear solution. The above prepared nitrosyl sulfuric acid was cooled and then added with efficient stirring to a solution of 4-cyanoaniline (1.06 g, 0.01 mol) in 15 ml glacial acetic acid at 0°-5°C. After addition, the mixture was stirred for 15 min. more and checked for excess of nitrous acid using starch iodide paper. The excess of nitrous acid was destroyed by the addition of urea.
Naptho [1,8-cd] dithiole (1.9 g 0.01 mole) was heated hi 30 ml glacial acetic acid until it dissolved completely and then the solution was cooled to 5°C. The above diazo solution was then added slowly to this solution under stirring and kept at 10°C for 30 min. The pH was brought to 5 by addition of sodium acetate. The ice bath was removed, the mixture allowed to come to room temperature and stirred further for 2 hr. It was poured into ice water (100 ml) and extracted with ethyl acetate (4 x 25 ml). The organic layer was washed with water and dried over sodium sulphate. Solvent was removed from
organic layer and residue was subjected to column chromatography through silica gel using petroleum ether - ethyl acetate (1:1) as eluent. Yield of monoazo dye : 65% (m.p. 288°-290°C).
The dyes prepared by the present invention maybe applied on polyester fibre by the process mentioned below.
Dispersions of the dyes were prepared by milling 1 g of the dye, 1 g of Tamol NNO (dispersing agent) in water 25 ml in a glass tube containing steel rods for 48 h. The 1% dispersion of these dyes were used as stock solution for dyeing polyester fiber.
The dye bath was set with 1% dispersion, 5% unisperse P ( a heat resistant leveling agent) and 1% acetic acid keeping the material liquor ratio 1 : 100. The material was entered at 60°C and the temperature raised to 130°C in 30 min. The dyeing was continued at 130°C for one more hour. After cooling the dyeings were taken out and given treatment with mixed solutions of sodium bisulfite 2% w/v and sodium hydroxide
4% w7v at 70°C for 15 min. Finally, the dyeings were rinsed well with water and dried at 60°C.
t The dyed polyester fiber was tested for sublimation and light fastness properties and were found to be promising. In particular,the dyes imparting blue-green and violet shades (Examples 1&2) exhibited very good light and sublimation fastness properties. Overall, all the dyes showed very good sublimation fastness properties whereas, light fastness varied from moderate to very good. The fastness properties can be further improved by applying the dyes using thermo-fixation process instead of high temperature high pressure dyeing technique used in the present disclosure.
The advantages of the present invention
1) This is the first disclosure of an efficient synthesis and study of dyeing
characteristics of new disperse dyes derived from naphtho[l,8-cd] dithiole as a
coupling component.
2) The products are pure enough and do not need further purification.
3) The dyes are:obtained in very good to excellent yields.
4) No sophisticated and moisture sensitive chemicals are used in the synthesis.
5) No side products are obtained in all the reactions.
6) The reactions are regioselective.
7) The reaction is very clean and work up involves minimum effort.
8) The dyes obtained from naptho [1,8-cd] dithiole as coupling component imparted
bright blue to blue-green shades on polyester with very good light and
sublimation fastness properties.
9) The azo dyes containing other substituents like nitro group can be used as a
starting material for the synthesis of cationic dyes.
10) Naptho [1,8-cd] dithiole enters readily into the azo coupling reaction not only
with such active diazonium ions as nitro and dinitro benzene diazonium salt but
also with unsubstituted benzene diazonium ion.
11) The high polarisability of the chromophoric systems make them potential
molecules for having non-linear optical (NLO) properties and as organic semi
conductors.
12) The dyes may also find use as speciality colorants for plastics.

We claim :
1. A process for the preparation of novel disperse dyes having general formula II from naphtho [1,8-cd] dithiole of formula I wherein R is a substituted cyano phenyl, cyano nitro phenyl, alkoxy phenyl, alkyl nitro phenyl, halo phenyl or halo nitro phenyl which comprises, treating a substituted aromatic amine with a diazotising agent in an acidic medium at a temperature in the range of -20° to 30°C, coupling with an organic acid solution of naphtha [1,8-cd] dithiole at a temperature ranging from -20° to 30°C, maintaining the pH of the above said reaction mixture ranging between 4 to 5 by adding a buffer under constant stirring for a period ranging from 2-6 hrs., quenching the reaction with water and separating the compound by conventional methods like extraction, distillation,
(Formula Removed)
FORMULA II
2. A process as claimed in claim 1, wherein the substituted aromatic amine used is selected from the group consisting of substituted cyano phenyl amine such as 4-cyano phenyl amine, substituted cyano nitro phenyl amine such as 2-cyano-4-nitro phenyl amine, substituted alkoxy nitro phenyl such as 4-methoxy-2 nitro phenyl, substituted helo phenyl amine selected from 3-chloro-4-flouro phenyl amine, 2-flouro phenyl amine and 2,4 dichloro phenyl amine, substituted alkyl nitro phenyl amine such 4 methyl-3 nitro phenyl amine and substituted halo nitro
amine such as 4-chloro-2 nitro phenyl amine.
A process as claimed in claims 1 & 2, wherein the diazotising agent used is
a mineral acid solution of alkali metal nitrite selected from the group consisting of
sodium nitrite, potassium nitrite and lithium nitrite preferably sodium nitrite.
A process as calimed in claims 1-3, wherein the mineral acid used is
selected from sulphuric acid and hydrochloric acid preferably sulphuric acid.
A process as calimed in claims 1 to 4, wherein the organic acid used is
selected from acetic acid and propionic acid preferably acetic acid.
A process as claimed in claims 1-5, wherein the buffer used is an alkali
metal acetate selected from sodium acetate and potassium acetate, preferably
sodium acetate.
A process for the preparation of novel disperse dyes from naphtho [1,8-cd]
dithiole as fully described hereinbefore with reference to the examples and
evening accompanying this .

Documents:

1075-del-2000-abstract.pdf

1075-del-2000-claims.pdf

1075-del-2000-correspondence-others.pdf

1075-del-2000-correspondence-po.pdf

1075-del-2000-description (complete).pdf

1075-del-2000-form-1.pdf

1075-del-2000-form-19.pdf

1075-del-2000-form-2.pdf

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Patent Number

221993

Indian Patent Application Number

1075/DEL/2000

PG Journal Number

32/2008

Publication Date

08-Aug-2008

Grant Date

14-Jul-2008

Date of Filing

29-Nov-2000

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG NEW DLEHI- 110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KUMAR VENKATARAMAN SRINIVASAN	NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA.
2	THOMAS DANIEL	NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA.
3	RAJAGOPAL JAGANNATH LAHOTI	NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA.
4	VINCENT PAUL SWAMY	NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA.
5	RAMAVARAMA RAJAGOPAL	NATIONAL CHEMICAL LABORATORY, PUNE-411008, MAHARASHTRA, INDIA.

PCT International Classification Number

C09B 3/70

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA