Title of Invention

AN IMPROVED PROCESS TO PREPARE 2-THIOCYANOMETHYL-THIOBENZOTHIAZOLE

Abstract The present invention relates to an improved process of preparing 2-thiocyanomethlthiobenzothiazole comprising reacting chlorobomomethane with ammonium thiocyanate to form chloromethylthiocyanate which is further reacted in-situ with sodium salt of 2- mercaptobenzothiazole in presence of suitable solvents such as carbontetrachloride, methylenedichloride, chloroform, toluene, xylene, isopropyl alcohol, acetone, methanol at temperature between 20-30 degree/C to give 2-thiocyanomethylthio-benzothiazole at least 98% purity. The present process is economical, safer and environment friendly. The purpose of this invention is useful as preservative for tanned leather and also very useful for prevention of mould growth on lumber and other surfaces and useful as microbiocide in pulp and paper industry ad water treatment industry.
Full Text AFORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
"AN IMPROVED PROCESS TO PREPARE 2 -THIOCYANOMETHYLTHIOBENZOTHIAZOLE""

2. APPLICANT
(a) NAME

SUDARSHAN CHEMICALS INDUSTRIES LTD.

(b) NATIONALITY : An Indian Company registered under the provisions of
the Companies Act, 1956

(c) ADDRESS

162, Wellesley Road, PUNE-411Q0L Maharashtra State, hidia

3. PREAMBLE TO THE DESCRIPTION

PROVISIONAL
The following specification describes the
/
mvention.

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

4. DESCRIPTION: Starts fi-om page 2.
5. CLAIMS : Given on page no.9
6. DATE AND SIGNATURE : On page No.9 of the Complete Specification.
7. ABSTRACT OF THE INVENTION: Gjven on separate page

GRANTED


26-4-2005
ORIGINAL

The present invention relates to a process for the preparation of 2-thiocyahome;thylthid-be:rizothiazole(TCMTB).
More particularly it relates to a process to prepare 2-thiocyahOmethylthiobehzothiazole (TCMTB) by reacting •Chlordbfohlbmethahe with alkali metal salt of thiocyahate of ammonium thoicyanate to forth Chloromethylthiocyanate, which is theh reacted ih-situ with alkali metal salt of 2-rhefcaptdbehzbthiazole; in a suitable sblveht to give TCMTB of rhiriimuni 98% purity.
2- Thibcyanomethylthiobehzothiazble (TCMTB) represented as under vide formula 1 is a useful fungicide, which is used as preservative for tanned leather; It is very useful for pfeveritibh of mould growth oh litmbbf and other suffices. It is also used as fhicfbbibcide ifi pulp and paper industries and water treatment industries.

Prior art
111 prior art theife are viarious processes to prepare TCMTB. which are granted patent by the United States Patent & Trademark Office and Japanese Patent Office as described belb\v;
US 3.463,785
In fliis process, chlbfbniethyl fhibcyariate was reacted with sbdiuhi 2-ihefc;aL{Jto behzbthiazble to fbffh TCMTB.Prbebss accbrdihg to this patent fequifes vefy Ibng reactibh tirttb ( 15 days) with less yield.

US3.520,976
US3,520,976 describes preparation of 2-chloromethylthiobenzothiazole from alkali metal salt of 2-mercaptobenzothiazole and large excess of bromochloromethane (10 mole per mole of 2-mercaptobenzothiazole). 2-chloromethylthiobenzothiazole was then reacted with ammonium thiocyanate to form 81.5% pure TCMTB using acetone as solvent. However, side products were 18-20% by this process. Therefore, the disadvantage was that the yield was not good and adequate.
US Patent No.4J55,609
This patent describes a process in which 2-chloromethylthiobenzothiazole was reacted with alkali metal thiocyanate or ammonium thiocyanate using water as solvent in presence of phase transfer catalyst. Reaction was carried out at a relatively high temperature and for a longer time in order to obtain good yield. Major disadvantage of this process is the decomposition of TCMTB in presence of water at high temperature.
US Patent No.5,073.638
This patent describes the preparation of TCMTB by reacting 2-chloromethylthiobenzothiazole in presence of at least one glycol ether as solvent for reaction with either an alkali metal thiocyanate or ammonivim thiocyanate at temperature in the range of 60-80°C. 90% yield was reported by this process. However, this process has disadvantage of decomposition of TCMTB due to higher temperature and longer reaction time.
Japanese Patent Application No.60-132971
This patent discloses the synthesis of TCMTB by reacting chloromethylthiocyanate with a water soluble salt of mercaptobenzothiazole in presence of water and a phase transfer catalyst.

The major disadvantage of this: process is that chloromethyl thiocyanate is a moisture sensitive molecule, which decomposes in water.
It is, therefore, a principal object of the pressent invention to obviate the disadvantages of the prior art processes and provide an improved process for the preparation of TCMTB.
It is another object of the present invehtion to provide an ecpnomical arid clean process for preparation of TCMTB.
Detailed description of the dreferred embodiments
The preserit invention relates to the preparation of TCMTB in high yield and high purity, by reactirtg Chldrobromomethane with alkali metal thidcyanate dr ammonium thiocyanate folldwed by alkali metal salts, more preferably the sodium salt of 2-niiercapto berizdthiazole in Single pot in presence of organic solvents preferably carbon tetra chldride, methylienedichlonde, chloroform, toIuene xylene isopropyl alcohol acetoiie and rnetliandl.
The reactions are carried out at much lower teniperatiire iti the range df 30-50°C than that in US Patent no. 5073638 to avoid decoimposition df TCMTB due to heating.
Siiide chloromethylthiocyanate is a high lachrymator add fighly toxic at a very low concentrations, the present invention aims at one pot synthesis of TCMTB starting
from bromocholromethane without isolating chloromethylthiocyanate.
Thus it is also the object of the presenit invention not to islate chloromethlylthiocyanate so that its ill effects can be avdided.
The preserit invention requires at least 1.0-1.2 mole of chlorobromomethane per mole of alkalii matel thoicyanate or ammonium thoicyanate as against 10 riidle reported

in earlier patents. Thus, the quantity of the effluent required is reduced considerably and thereby the entire process to prepare TCMTB is reduced significantly.
Organic solvents preferably carbontetrachloride, methylenedicWoride, chloroform, toluene, xylene, isopropyl alcohol, acetone, methanol is required as solvent in the reaction.
The present invention requires 1.0-1.02 mole of alkali metal salt of mercaptobenzothiazole per mole of alkali metal thiocyanate or ammonium thiocyanate. Chloromethylthiocyanate is not isolated in present invention hence safer and environment friendly process. Yield has also been improved by this process.
Since the present invention does not require water as solvent, purity of TCMTB is significantly improved as against the process mentioned in Japanese patent application no.60-132971 because chloromethylthicyanate and TCMTB are highly reactive towards water.
ANALYTICAL DATA FOR TCMTB
A-4 PROCEDURE
A-4.1 Preparation of the Mobile Phase
Mix acetonitrile and water in proportion 85:15(v/v) and pass through membrane filter
(0.45) under vacuum. Homogenize the mixture using a magnetic stirrer and allow to
attain the room temperature.
A-4.2 Preparation of Internal Standard Solution
Weigh out accurately 2.5g of Dibutyl phthalate into a 50ml volumetric flask. Make up
the volume upto mark with dimethyl sulfoxide. Shake well to homogenize the solution.
A-4.2 Preparation of Standard /Sample Solntion
Weigh accurately about 0.03 g of TCMTB Standard/Sample into a 25ml volumetric
flask. Add 5ml of internal standard solution into the same flask and make up the
volume upto the mark with dimethyl sulfoxide.

A-4.4 Estimation :
A-4,4.1 Inject 5 of the reference standard solution followed by the sample solution. Measure the peak areas of internal standard and TCMTB peaks and compute the percentage of TCMTB as given in A-5.
A-4.4.2 Retention times (Guide values)
Internal Standard (Dibutyl Phthalate ) -5.lmin.
TCMTB - 3.4 min.
Total run time - 10 min.
A-5 CALCULATION ;
A3 X A2 X Ml X P TCMTB content, percent by mass = A4 x Al x M2
Where,
Al = The area of TCMTB peak in standard solution
A2 = The area of TCMTB peak in sample solution
A3 = The area of Dibutyl Phthalate peak in standard solution
A4 = The area of Dibutyl Phthalate peak in sample solution
Ml = The mass in g of the standard
M2 = The mass in g of the sample
P= The percentage purity of the standard TCMTB
CALCULATIONS:
TCMTB BXNo.44
As per A-5,
TCMTB Content,% by mass = A3 x A2 x Ml x P
A4 X Al X M2
= 48.953 X 47.396 x 0.0187 x 99 51.305x49.675x0.0171

TCMTB Content,% by mass = 98.56%
Where,
Al = The area of TCMTB peak in standard solution
A2 = The area of TCMTB peak in sample solution
A3 = The area of Dibutyl Phthalate peak in standard solution
A4 = The area of Dibutyl Phthalate peak in sample solution
Ml = The mass in gram of the standard
M2 = The mass in gram of the sample
P= The percentage purity of the standard TCMTB.
Thus, according to this invention, an improved process for preparing 2-thiocyanomethylthiobenzothiazole of the formula 1

Formula 1 comprises -
reacting chlorobromomethane with ammonium thiocyanate to form chloromethylthiocyanate, which is then reacted in-situ with sodium salt of 2-merecaptobenzothiazole in presence of suitable solvents herein described at a temperature between 30-50°C to give TCMTB of at least 98% purity.
The invention is described below in details :
Alkali metal thiocyanate or ammonium thiocyanate and bromochloromethane are reacted in suitable solvent as mentioned at 45-50°C for 4-5 hours. Excess bromochloromethane is recovered along with solvent under vacuum maintaining temperature below 50°C under stirring. Recovered bromochloromethane and solvent is recycled. Sodium salt of 2-merecaptobenzothiazole is added in same reaction pot along with suitable solvent. Reaction mixture is further heated to 45-50°C within 4-5 hours

for completion of reaction. Reaction mixture is filtered and washed with water. Solvent is recovered under vacuum and TCMTB is obtained with at least 98% purity.
The following illustration discloses the nature of invention clearly, though it is not limited to the specific conditions or details set forth in the examples.
Example 1
Preparation of thiocyanomethylthiobenzothiazole (TMTCB) A 2-litre four neck round bottom flask equipped with a stirrer, condenser and thermowell. 81 gm (1.0 mole) sodium thiocyanate, 155.4 gm (1.2 mole) bromochloromethane and 600 gm (10.0 mole) isopropyl alcohol are added in the flask under continuous stirring. Reaction is carried out at 45-50°C for 4-5 hours under stirring. Excess bromochloromethane is recovered along with isopropyl alcohol under vacuum maintaining temperature below 50°C under stirring. Recovered bromochloromethane and isopropyl alcohol is recycled in next batch. 700 gm (4.54 mole) of carbontetrachloride and 189 gm (1.0 mole) sodium salt of 2-mercaptobenzothiazole are added in the same reaction pot over a period of 10 minutes at 45-50°C within 4-5 hours for complete conversion. Reaction mixture is filtered and washed with water. Carbontetrachloride is recovered under vacuum. 226 gm TCMTB (95% of theory) is obtained with purity of at least 98%.

WE CLAIM:
1. An improved process for preparing 2-thiocyanomethylthiobenzothiazole of the
formula 1

Formula 1
comprising -
reacting chlorobromomethane with ammonium thiocyanate to form chloromethylthiocyanate, which is then reacted in-situ with sodium salt of 2-merecaptobenzothiazole in presence of suitable solvents herein described at a temperature between 30-50°C to give TCMTB of at least 98% purity.
2. A process as claimed in claim 1, wherein the concentration of chlorobromomethane per mole of alkali metal thiocyanate or ammonium thiocyanate is 1.0 to 1.20 moles.
3. A process as claimed in claim 1, wherein the concentration of alkali metal thiocyanate or ammonium thiocyanate is 1.0 to 1.20 moles.
4. A process as claimed in claim 1, wherein the solvents or diluents are carbontetrachloride, methylenedichloride, chloroform, toluene, xylene, isopropyl alcohol, acetone, methanol,
5. A process as claimed in claim 1, wherein the entire reaction is carried out in-situ and Chloromethylthiocyanate as an intermediate is not isolated.
6. A process as claimed in claim 1, wherein the yield of TCMTB is 95% with purity of at least 98%.
7. A process as claimed in claim 1, wherein the reaction is carried out at atmospheric pressure.
Dated this 18th Day of June, 2004
M.D.BHATE
AGENT FOR APPLICANT

Documents:

672-mum-204-abstract (26-04-2005).pdf

672-mum-204-cancelled page (26-04-2005).pdf

672-mum-204-claim(granted)-(26-04-2005).pdf

672-mum-204-correspondence(26-04-2005).pdf

672-mum-204-correspondence(ipo)-(30-09-2004).pdf

672-mum-204-form 1(21-06-2004).pdf

672-mum-204-form 19(18-08-2004).pdf

672-mum-204-form 2(granted)-(26-04-2005).pdf

672-mum-204-form 3(22-06-2004).pdf

672-mum-204-power of attorney(21-06-2004).pdf


Patent Number 212029
Indian Patent Application Number 672/MUM/2004
PG Journal Number 13/2008
Publication Date 28-Mar-2008
Grant Date 13-Nov-2007
Date of Filing 21-Jun-2004
Name of Patentee SUDARSHAN CHEMICAL INDUSTRIS LTD.
Applicant Address 162, WELLESLEY ROAD, PUNE-411001
Inventors:
# Inventor's Name Inventor's Address
1 MAHENDRA PRATAP SINGH C/O SUDARSHAN CHEMICAL INDUSTRIS LTD. 162, WELLESLEY ROAD, PUNE-411001
2 DEEPIKA BUDDHIRAJU C/O SUDARSHAN CHEMICAL INDUSTRIS LTD. 162, WELLESLEY ROAD, PUNE-411001
3 VEERINDER KUMAR KOUL C/O SUDARSHAN CHEMICAL INDUSTRIS LTD. 162, WELLESLEY ROAD, PUNE-411001
PCT International Classification Number C07D277/74
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA