FORM-2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
Process for the preparation of 3-chloroiminodibenzyl
APPLICANT:
HERBERT BROWN PHARMACEUTICAL & RESEARCH LABORATORIES
W-256/257/258A, M.I.D.C. Phase II, Shivaji Udyog Nagar, Dombivli (E)-421203, District- Thane, Maharashtra, India.
Indian Company incorporated under the Companies Act 1956
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to a process for the preparation of substantially pure 3-chloroiminodibenzyl of structural Formula I, an intermediate of antidepressant drug Clomipramine hydrochloride.

BACKGROUND OF THE INVENTION
Clomipramine hydrochloride is chemically, 3-(3-chloro-10,ll-dihydro-5H-dibenzo[b,f]azepin-5-yl)-N,N-dimethylpropan-l-amine hydrochloride and has the structural Formula II. It is a tricyclic antidepressant and is considered to be "the most powerful antidepressant".

A number of methods for the preparation of Clomipramine hydrochloride are reported in literature but the simplest synthetic route is through formation of 3-chloroiminodibenzyl, an intermediate. The increasing demand for Clomipramine hydrochloride are therefore increasing the demand for industrial manufacturing of 3-chloroiminodibenzyl.

Few methods and processes for the preparation of 3-chloroiminodibenzyl are known in literature, some of these methods are summarized here.
US3056774 discloses a process for the preparation of 3-chloroiminodibenzyl by hydrolyzing the 5-acetyl-3-chloroiminodibenzyl with potassium hydroxide in presence of methanol as a solvent. The 5-acetyl-3-chloroiminodibenzyl, used as starting material, was prepared by condensation of 5-acetyliminodibenzyl with acetyl chloride/acetic anhydride in presence of carbon disulfide as solvent, converting the thus formed 3,5-diacetyliminodibenzyl by means of hydrazoic acid into 3-acetamido-5-acetyliminodibenzyl, partially hydrolyzing 3-acetamido-5-acetyliminodibenzyl to 3-amino-5-acetyliminodibenzyl, converting this to diazonium salt followed by reacting the diazonium salt with cuprous chloride as per Sandmeyer's reaction to obtain 5-acetyl-3-chloroiminodibenzyl. The process involves use of hazardous solvent like carbon disulfide in the process and hence this process is not feasible on industrial scale. Scheme I given below depicts the process.


US3056776 discloses a process for the preparation of 3-chloroiminodibenzyl by eliminating one chlorine atom by catalytic hydrogenation from 3,7-dichloroiminodibenzyl in presence of solvent like methanol and dioxane. The process involves separation of 3-chloroiminodibenzyl by fractional distillation from the mixture of close boiling components like iminodibenzyl and 3,7-dichloroiminodibenzyl. Scheme II given below depicts the process described above.

US3016373 discloses a process for the preparation of 3-chloroiminodibenzyl. The process involves conversion of 3-chloro-9-acridane methanol to 3-chlorodibenz[b,f]azepine by heating with xylene/ chlorobenzene in presence of phosphorous pentaoxide at 125-175°C for 1 -6 hours followed by catalytic hydrogenation of 3-chlorodibenz[b,f]azepine to obtain 3-chloroiminodibenzyl. The 3-chloro-9-acridane methanol used in the process is prepared by starting with 3,9-dichloroacridine. The 3,9-dichloroacridine was converted to 3-chloro-9-cyanoacridine by reacting with sodium cyanide. The cyano derivative thus formed was hydrolyzed using sulfuric acid and the acid amide formed was treated with nitrous acid to form 3-chloro-9-acridine carboxylic acid. The acid was reacted with excess of thionyl chloride and the resulting acid chloride was esterified with ethanol to give ethyl 3-chloro-9-acridine carboxylate. Reduction of the ester with lithium aluminium hydride yields the 3-chloro-9-acridane methanol. Scheme III given below depicts the reaction described above.


The disadvantages of this process can be listed as below
i) tedious and laborious process as it involves multiple steps
ii) temperature required is as high as 175°C
iii) use of hazardous reagents like sodium cyanide, thionyl chloride and
lithium aluminium hydride iv) use of various reagents and isolation of each intermediate in the process
increases the overall cost of the process
HU67041 describes a process for the preparation of 3-chloroiminodibenzyl by one-step diazotization/Sandmeyer reaction of 5-acetyl-3-aminoiminodibenzyl with isopentyl nitrite and anhydrous C11O2 in presence of acetonitrile as a solvent. Use of expensive reagent like isopentyl nitrite makes the process less feasible on industrial scale. Furthermore, use of water miscible solvent like acetonitrile makes recovery and reuse of solvent difficult. Scheme IV depicts the reaction of the process described.


Apart from above discussed references some of the other references related to process for the preparation of 3-chloroiminodibenzyl includes Journal of Organic Chemistry 26, 135-8 (1961), Journal fuer Praktische Chemie 339(6), 587-589 (1997), Journal of Heterocyclic Chemistry 36(1), 57-64 (1999), US3033866, JP48080547, JP 48081844, US 4013639 and JP53098984.
CN102010349 discloses a method for the synthesis of 5-acetyl-3-chloroiminodibenzyl wherein a raw material iminodibenzyl is reflux-acylated with acetic anhydride in acetic acid in presence of perchloric acid as catalyst, followed by nitrating with 96% nitric acid to obtain 5-acetyl-3-nitroiminodibenzyl. The 5-acetyl-3-nitroiminodibenzyl is then reduced with hydrazine hydrate in presence of anhydrous ferric chloride as catalyst and activated carbon as co-catalyst to obtain 5-acetyl-3-aminoiminodibenzyl. The 5-acetyl-3-aminoiminodibenzyl was diazotized by reacting with sodium nitrite and hydrochloric acid in water solution to obtain diazonium salt/HCl solution and finally diazonium salt/HCl solution was reacted with cuprous chloride in HCl/water solution to obtain final product. The process provided yields of 51% of 5-acetyl-3-chloroiminodibenzyl. The above mentioned reaction is shown in Scheme V.


Even though above prior art processes reports method for the preparation of 3-chloroiminodibenzyl, each process had some drawbacks with respect to use of solvents and reagents in reaction, purity of final product and feasibility on industrial scale. By keeping in view the drawbacks of the prior art, the inventors of the present invention have rationally designed a simple, economic, environment friendly and industrially feasible process for the preparation of 3-chloroiminodibenzyl. Furthermore, the 3-chloroiminodibenzyl obtained by the process of present invention has GC purity of more than 99 %
OBJECT OF THE INVENTION
1. It is an object of the present invention to provide an improved process for the preparation of 3-chloroiminodibenzyl by using indigenously available starting material.

2. Yet another object of the present invention is to provide an improved process for the preparation of 3-chloroiminodibenzyl, which gives the product of high purity and in good yield.
3. Another object of the present invention is to provide an environment-friendly process for the preparation of 3-chloroiminodibenzyl without using any hazardous chemicals.
4. Still another object of the present invention is to provide an improved process for the preparation of 3-chloroiminodibenzyl, which can easily be up-scaled and is cost effective
SUMMARY OF THE INVENTION
According to an aspect of the present invention there is provided an improved process for the preparation of 3-chloroiminodibenzyl of Formula I, from 5-acetyl-3-nitroiminodibenzyl

comprising,
i) reducing 5-acetyl-3-nitroiminodibenzyl of Formula III in an alcohol in
presence of a metal catalyst under hydrogen pressure of about 2-6kg/cm2 at temperature of about 40-70°C for 4 to 8 hours


Formula III
ii) separating the metal catalyst by filtration, concentrating the thus formed filterate, adding water to yield 5-acetyl-3-aminoiminodibenzyl of Formula IV having GC purity of more than 98%

iii) reacting 5-acetyl-3-aminoiminodibenzyl of Formula IV with sodium
nitrite in presence of hydrochloric acid in water at temperature ranging
from 0-15°C to form a diazonium salt solution iv) insitu reacting the diazonium salt solution with cuprous chloride and
concentrated hydrochloric acid in presence of an organic solvent selected
from a hydrocarbon at 0-5°C followed by heating the mixture to 50-55°C
for 10 to 60 minutes v) separating an organic layer, subjecting the organic layer to charcoalization
and concentrating to isolate crude 5-acetyl-3-chloroiminodibenzyl of
Formula V having GC purity of more than 90%


vi) purifying the crude 5-acetyl-3-chloroiminodibenzyl by recrystallization
with an organic solvent to yield 5-acetyl-3-chloroimmodibenzyl of
Formula V having GC purity of more than 98% vii) hydrolyzing 5-acetyl-3-chloroiminodibenzyl of Formula V with an
aqueous alkali metal hydroxide in presence of n-butanol at temperature of
about 100-110°C for 4 to 6 hours under nitrogen atmosphere and
subsequently followed by addition of water viii) separating n-butanol layer from aqueous layer, concentrating the n-butanol
layer followed by addition of water to isolate crude 3-chIoroiminodibenzyl
of Formula I having GC purity of more that 98% ix) dissolving the crude 3-chloroiminodibenzyl in an alcohol at 50-55°C and
charcoalizing the solution at reflux temperature to obtain a charcoalized
solution x) concentrating the charcoalized solution of step ix) and isolating 3-
chloroiminodibenzyl of Formula I having GC purity of more than 99% by
addition of water
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to improved process for the preparation of 3-chloroiminodibenzyl, a key intermediate required for the preparation of Clomipramine hydrochloride.
According to an embodiment of the present invention there is provided an improved process for the preparation of 3-chloroiminodibenzyl of Formula I, from 5-acetyl-3-nitroiminodibenzyl


comprising,
i) reducing 5-acetyl-3-nitroiminodibenzyl of Formula III in an alcohol in
presence of a metal catalyst under hydrogen pressure of about 2-6kg/cm at temperature of about 40-70°C for 4 to 8 hours

ii) separating the metal catalyst by filtration, concentrating the thus formed filterate, adding water to yield 5-acetyl-3-aminoiminodibenzyl of Formula IV having GC purity of more than 98%

iii) reacting 5-acetyl-3-aminoiminodibenzyl of Formula IV with sodium nitrite in presence of hydrochloric acid in water at temperature ranging from 0-15°C to form a diazonium salt solution
iv) insitu reacting the diazonium salt solution with cuprous chloride and concentrated hydrochloric acid in presence of an organic solvent selected from a hydrocarbon at 0-5°C followed by heating the mixture to 50-55°C for 10 to 60 minutes

v) separating an organic layer, subjecting the organic layer to charcoalization and concentrating to isolate crude 5-acetyl-3-chloroiminodibenzyl of Formula V having GC purity of more than 90%

vi) purifying the crude 5-acetyl-3-chloroiminodibenzyl by recrystallization
with an organic solvent to yield 5-acetyl-3-chloroiminodibenzyl of
Formula V having GC purity of more than 98% vii) hydrolyzing 5-acetyl-3-chloroiminodibenzyl of Formula V with an
aqueous alkali metal hydroxide in presence of n-butanol at temperature of
about 100-110°C for 4 to 6 hours under nitrogen atmosphere and
subsequently followed by addition of water viii) separating n-butanol layer from aqueous layer, concentrating the n-butanol
layer followed by addition of water to isolate crude 3-chloroiminodibenzyl
of Formula I having GC purity of more that 98% ix) dissolving the crude 3-chloroiminodibenzyl in an alcohol at 50-55°C and
charcoalizing the solution at reflux temperature to obtain a charcoalized
solution x) concentrating the charcoalized solution of step ix) and isolating 3-
chloroiminodibenzyl of Formula I having GC purity of more than 99% by
addition of water
The present invention particularly relates to improved process for preparation of substantially pure 3-chloroiminodibenzyl with good yields. The process can be depicted in Scheme VI


According to an embodiment of the present invention, the alcohol used in step i) is selected from methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, preferably methanol or n-butanol is used.
The amount of alcohol used in step i) is in the range of 3 to 8 volumes, preferably 4 to 7 volumes.
In step i) the metal catalyst like Raney Nickel, Palladium is used, preferably Raney Nickel is used.
The amount of the metal catalyst used with respect to 5-acetyl-3-nitroiminodibenzyI is in the range of 2 to 8% w/w, preferably 4 to 6% w/w.
The 5-acetyl-3-nitroiminodibenzyl of Formula III is taken as the key starting material

for the present process and is prepared according to prior art processes, with minor modifications in order to provide final product in high quality and yield.
According to another embodiment of the present invention, the amount of water used in step ii) is in the range of 3 to 5 volumes.
According to another embodiment of the present invention, the molar ratio of sodium nitrite used in step iii) with respect to 5-acetyl-3-aminodibenzyl is in the range of 1 to 1.5.
The amount of concentrated hydrochloric acid used in step iii) with respect to 5-acetyl-3-aminodibenzyl is in the range of 3 to 5 volumes.
According to yet another embodiment of the present invention, the molar ratio of cuprous chloride used in step iv) with respect to 5-acetyl-3-aminoiminodibenzyl of Formula IV is in the range of 1 to 1.5.
The organic solvent used in step iv) is selected from a hydrocarbon such as toluene, xylene and the like, preferably toluene is used.
The amount of organic solvent used in step iv) with respect to 5-acetyl-3-aminoiminodibenzyl of Formula IV is in the range of 3 to 7 volumes.
According to an embodiment of the present invention, in step vi) the crude 5-acetyl-3-chloroiminodibenzyl is recrystallized using an organic solvent selected from an alcoholic solvent like methanol, ethanol, n-propanol, iso-propanol and n-butanol, a hydrocarbon solvent like toluene, hexane, heptane, cyclohexane, a halogenated hydrocarbon solvent like methylene chloride, chloroform or combination thereof.

Preferably, the crude 5-acetyl-3-chloroiminodibenzyl is recrystallized using single solvent like methanol or combination of two solvents like toluene-hexane or methylene chloride-hexane.
According to an embodiment of the present invention, in step vii) the alkali metal hydroxide like potassium hydroxide or sodium hydroxide is used, preferably sodium hydroxide is used.
The molar ratio of alkali metal hydroxide used with respect to 5-acetyl-3-chloroiminodibenzyl is in the range of 2 to 3.
The amount of water used in step vii) for preparing aqueous alkali metal hydroxide solution with respect to 5-acetyl-3-chloroiminodibenzyl is in the range of 0.4 to 0.5 volumes.
The amount of n-butanol used in step vii) with respect to 5-acetyl-3-chloroiminodibenzyl is in the range of 3 to 6 volumes.
The inventors of the present invention surprisingly found that, the hydrolysis of 5-acetyl-3-chloroiminodibenzyl with aqueous sodium hydroxide in presence of n-butanol gives better results in terms of yield and purity.
According to an embodiment of the present invention, the amount of water used in step viii) with respect to 5-acetyl-3-chloroiminodibenzyl is in the range of 1 to 4 volume.
According to yet another embodiment of the present invention, the alcohol used in

step ix) is selected from methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, preferably methanol or n-butanol is used.
The amount of alcohol used in step ix) is in the range of 5 to 7 volumes.
According to still another embodiment of the present invention, the amount of water used in step x) is in the range of 4 to 6 volumes.
It was observed by the inventors of present invention, that the present process ensures removal of impurities like 5-acetyliminodibenzyl of Formula VI, 5-acetyl-3,7-dinitroiminodibenzyl of Formula VII, 5-acetyl 3,7-diaminoiminodibenzyl of Formula VIII, 5-acetyl-3,7-dichloroiminodibenzyl of Formula IX, 3,7-dichloroiminodibenzyl of Formula X and 3-chIoroiminostilbene of Formula XI, to the extent of less than 0.1%.



The GC purity of 3-chloroiminodibenzyl of Formula I is determined using following
parameters:
Instrument : GC Agilent 7890 A
Column : HP-5, 30 m x 0.32mm ID, 0.25u.m capillary column
Column temperature : 150°C (2 min. hold) @15°C/min - 250°C
(1 min. hold) 15°C/min--300°C (18 min. hold)
Injector temperature : 280°C
Detector temperature : 300°C
Detector : FID
Carrier gas flow : 2.0 mi/min. (Split ratio: 1: 25)
Carrier gas : Nitrogen
Injection Volume : l.Oμl
Run time : 32 min.
The detail of the invention provided in the following examples is given by the way of illustration only and should not be construed to limit the scope of the present invention.
EXAMPLES
Example 1: Preparation of 5-AcetyI-3-nitroiminodibenzyl
To a suspension of iminodibenzyl (500g) in acetic anhydride (392g) was added sulfuric acid (10ml). The mixture was then heated to 100-110°C for 1 to 1.5 hours. After completion of reaction, the mixture was cooled to 50-60°C and water (25ml)

was added. The mixture was then allowed to cool to 25-30°C and the 5-acetyliminodibenzyl of Formula III formed, was insitu nitrated with 70% nitric acid (230.4g) in presence of acetic acid (600ml) and sulfuric acid (3136g) at temperature ranging from 0-15°C. The mixture was maintained at 0-5°C for 30 minutes. The reaction progress was monitored by using GC. After completion of the reaction, it was quenched by adding into ice-water followed by maintaining temperature 10-15°C for 1 hour. The precipitate obtained was filtered and washed with water. To the wet cake obtained was added water (5000ml) and pH of the slurry was adjusted to neutral using 10% sodium hydroxide. The crude 5-acetylnitroiminodibenzyl was filtered out, washed with water and dried under reduced pressure at 70-75°C. The crude product obtained was dissolved in methanol at reflux temperature and crystallized out by gradually cooling to 25-30°C. The product was once again recrystallized with methanol, isolated and dried under vacuum at 70-75°C to obtain 365g (50.5%) of pure 5-acetyl-3-nitroiminodibenzyl having GC purity of 99.03%. Melting Point: 156-157 °C GC-MS (m/z): 282 (M+), 241, 225, 193, 179, 165, 89.
Example 2: Preparation of 5-AcetyI-3-aminoiminodibenzyl
To a 5-acetyl-3-nitroiminodibenzyl (lOOOg) in methanol (6000ml) in a high pressure reactor was carefully added Raney Nickel (50g, 5%wt/wt) under nitrogen atmosphere. Subsequently, the reactor was flushed with nitrogen gas, followed by with hydrogen gas. The reaction mixture was subjected to hydrogenation at temperature of about 60-65°C under hydrogen pressure of about 3-6Kg/cm for about 6 to 8 hours. The reaction progress was monitored using GC. GC analysis after 6 hours, showed less than 0.5% of unreacted 5-acetyl-3-nitroiminodibenzyI. Upon completion of reaction, the catalyst was removed at 50-55°C by filtration and washed with methanol (500ml). The filterate was concentrated under reduced pressure until low volume slurry is obtained. To the slurry was added water (4000ml) and then one

volume water (i.e. 1000ml) was distilled out under vacuum to remove traces of
methanol. The mixture was then cooled to 25-30°C, filtered, washed with water and
the solid thus obtained was dried under vacuum at 70-75°C to afford 825g (92.31%)
of 5-acetyl-3-aminoiminodibenzyl having GC purity of 98.91%.
Melting Point: 148-149 °C
GC-MS (m/z): 252 (M+), 210 (Base peak), 193,180,167.
Example 3: Preparation of 5-Acetyl-3-aminoiminodibenzyl
To a 5-acetyl-3-nitroiminodibenzyl (650g) in n-butanol (3250ml) in a high pressure reactor was carefully added Raney Nickel (32.5g, 5%wt/wt) under nitrogen atmosphere. Subsequently, the reactor was flushed with nitrogen gas, followed by with hydrogen gas. The reaction mixture was subjected to hydrogenation at temperature of about 60-70°C under hydrogen pressure of about 3-6Kg/cm2 for about 6 hours. The reaction progress was monitored using GC. GC analysis after 6 hours, showed less than 0.5% of unreacted 5-acetyl-3-nitroiminodibenzyl. Upon completion of the reaction, the catalyst was removed at 50-60°C by filtration. The filterate was concentrated under reduced pressure to dryness. Then to the residue was added water (100ml) followed by distilling out water under vacuum to remove traces of n-butanol. To the residue was again added water (1300ml), stirred for 1 hour at 25-30°C, filtered, washed with water and the solid thus obtained was dried under vacuum at 70-75°C to afford 544g (93.50%) of 5-acetyl-3-aminoiminodibenzyl having GC purity of 99.25%.
Example 4: Preparation of 5-Acetyl-3-chloroiminodibenzyI
To a solution of water (200ml) and concentrated hydrochloric acid (350ml) at 10-15°C was added 5-acetyl-3-aminodibenzyl (250g). The mixture was then cooled to 0-5°C under nitrogen atmosphere. To the mixture was then drop-wise added a 0~5°C precooled aqueous solution of sodium nitrite (75g sodium nitrite in 200ml water).

The mixture was stirred at 0-5°C for 1 hour to obtain a diazonium salt solution. The diazonium salt solution was added drop-wise to a pre-cooled (0-5°C) solution of concentrated hydrochloric acid (625ml), cuprous chloride (122.37g) and toluene (1250ml) by maintaining the temperature 0-5°C. The mixture was then stirred at the same temperature for 30 minutes and then was heated to 50-55°C for 30 minutes. After completion of the reaction, the organic and the aqueous layer were separated at about 50-55°C. The aqueous layer was washed with toluene (250ml) and the washings were combined with the organic layer. The combined organic layer was washed with water at 50-55°C. Subsequently, the combined organic layer was washed with 5% aqueous sodium bicarbonate solution and brine solution at 25-30°C. The organic layer was then charcoalized at 50-55°C for 1 hour, filtered through hyflo and washed with hot toluene. The charcoalized organic layer was concentrated to obtain 252g of crude 5-acetyl-3-chloroiminodibenzyl having GC purity of more than 90%. The crude 5-acetyl-3-chloroiminodibenzyl was dissolved in methanol (500ml) at reflux temperature and the product was crystallized out by gradually cooling to 0-5°C. The product was filtered to obtain a wet cake. The methanol purification process was once again repeated with wet cake, the final product obtained was isolated and dried under vacuum at 70-75°C to afford 171g (63.5%) of 5-acetyl-3-chloroiminodibenzyl having GC purity of 98.97%. Melting Point: 118-125 °C GC-MS (m/z): 273, 271 (m+), 231, 229 (Base peak), 216, 214, 194.
Example 5: Purification of crude 5-Acetyl-3-chloroiminodibenzyl
The procedure is carried out as in example 4, starting with 200g of 5-acetyl-3-aminoiminodibenzyl, except for the 193g of crude 5-acetyl-3-chloroiminodibenzyl having GC purity of more than 90% obtained after concentrating the charcoalized solution was purified using following process. The crude 5-acetyl-3-chloroiminodibenzyl (193g) was dissolved in toluene (154ml) at

70-80°C, charcoalized and the product was crystallized out by slow addition of hexane (617ml). The purification process was repeated, the solid obtained was filtered and dried under vacuum at 70-75°C to afford 158.26g (73.78%) of 5-acetyl-3-chloroiminodibenzyl having GC purity of 99.06%.
Example 6: Preparation of 3-Chloroiminodibenzyl
To a slurry of 5-acetyl-3-chloroiminodibenzyl (160g) in n-butanol (640ml) was added aqueous sodium hydroxide solution (59g of sodium hydroxide in 64ml of water) and the mixture was heated to 105-110°C for 6 hours in a nitrogen atmosphere. The reaction progress was monitored using GC. After 6 hours, the GC analysis showed less than 0.5% of 5-acetyl-3-chloroiminodibenzyl. To the reaction mixture was then added water (800ml) and stirred for 30 minutes. The aqueous layer was separated and washed with n-butanol, the washings were collected and combined with the organic layer. The combined organic layer thus formed, was concentrated under vacuum at 55-60°C and trapped n-butanol was co-evaporated with water (240ml) to form a residue. To the residue was then added water (320ml), stirred for 30 minutes, the solid was filtered out, washed with water and dried at 55-60°C to obtain 133g (98.25%) of crude 3-chloroiminodibenzyl having GC purity of 98.85%. The crude 3-chloroiminodibenzyl was charcoalized in methanol (768ml) at 50-55°C, the methanolic solution was then concentrated to low volume and the product was crystallized out by adding water (640ml). The solid was filtered out, washed with water and dried under vacuum at 55-60°C to afford 125g (92.41%) of 3-chloroiminodibenzyl having GC purity of 99.18%. Melting Point: 86-87 °C Moisture Content (KF): 0.04% Loss on Drying: 0.12%
1H NMR in CDC13 (δ ppm, 400MHz): 7.10-7.06 (m, 1H, ArH), 7.04 (dd, 1H, ArH), 6.94-6.92 (m, 1H, ArH), 6.82-6.78 (m, 1H, ArH), 6.72-6.69 (m, 3H, ArH), 5.95 (s,

lH,NH),3.0(t,4H,2 x ArCH2).
IR (KBr): 3373.61, 3059.20, 3028.34, 2947.33, 2912.61, 2887.53, 2852.81, 2841.24, 1612.54, 1581.68, 1525.74, 1489.10, 1440.87, 1394.58, 1352.14, 1334.78, 1319.35, 1294.28, 1273.06, 1244.13, 1209.41, 1193.98, 1157.33, 1118.75, 1095.60, 1055.10, 1049.31, 952.87, 846.78,7 92.77,746.48,734.90,597.95cm-1.
GC-MS (m/z): 231/229 (Base peak), 216/214, 194, 178, 165, 152, 139, 113, 100,97, 84.
GC Analysis of 3-Chloroiminodibenzyl:
Iminodibenzyl: 0.050% 5-Acetyliminodibenzyl: 0.044% 5-Acetyl-3-chloroiminodibenzyl; 0.085% 3-Chloroiminodibenzyl: 99.18% 3.7-Dichloroiminodibenzyl: 0.069% 3-Chloroiminostilbene: Nil

We claim
1. An improved process for the preparation of 3-chloroiminodibenzyl of Formula I,
from 5-acetyl-3-nitroiminodibenzyl

comprising,
i) reducing 5-acetyl-3-nitroiminodibenzyl of Formula III in an alcohol in
presence of a metal catalyst under hydrogen pressure of about 2-6kg/cm at temperature of about 40-70°C for 4 to 8 hours

ii) separating the metal catalyst by filtration, concentrating the thus formed filterate, adding water to yield 5-acetyl-3-aminoiminodibenzyl of Formula IV having GC purity of more than 98%

iii) reacting 5-acetyl-3-aminoiminodibenzyl of Formula IV with sodium nitrite in presence of hydrochloric acid in water at temperature ranging from 0-15°C to form a diazonium salt solution
iv) insitu reacting the diazonium salt solution with cuprous chloride and

concentrated hydrochloric acid in presence of an organic solvent selected from a hydrocarbon at 0-5°C followed by heating the mixture to 50-55°C for 10 to 60 minutes v) separating an organic layer, subjecting the organic layer to charcoalization and concentrating to isolate crude 5-acetyl-3-chloroiminodibenzyl of Formula V having GC purity of more than 90%

vi) purifying the crude 5-acetyl-3-chloroiminodibenzyl by recrystallization
with an organic solvent to yield 5-acetyl-3-chloroiminodibenzyl of
Formula V having GC purity of more than 98% vii) hydrolyzing 5-acetyl-3-chloroiminodibenzyl of Formula V with an
aqueous alkali metal hydroxide in presence of n-butanol at temperature of
about 100-110°C for 4 to 6 hours under nitrogen atmosphere and
subsequently followed by addition of water viii) separating n-butanol layer from aqueous layer, concentrating the n-butanol
layer followed by addition of water to isolate crude 3-chloroiminodibenzyl
of Formula I having GC purity of more that 98% ix) dissolving the crude 3-chloroiminodibenzyl in an alcohol at 50-55°C and
charcoalizing the solution at Teflux temperature to obtain a charcoalized
solution x) concentrating the charcoalized solution of step ix) and isolating 3-
chloroiminodibenzyl of Formula I having GC purity of more than 99% by
addition of water

2. The process as claimed in claim 1, wherein the alcohol used in step i) or step ix) is selected from methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, preferably methanol or n-butanol is used.
3. The process as claimed in claim 1, wherein in step i) the metal catalyst like Raney Nickel, Palladium is used, preferably Raney Nickel is used.
4. The process as claimed in claim 1, wherein the molar ratio of sodium nitrite used in step iii) with respect to 5-acetyl-3-aminoiminodibenzyl is in the range of 1 to 1.5.
5. The process as claimed in claim 1, wherein the molar ratio of cuprous chloride used in step iv) with respect to 5-acetyl-3-aminoiminodibenzyl of Formula IV is in the range of 1 to 1.5.
6. The process as claimed in claim 1, wherein the organic solvent used in step iv) is selected from a hydrocarbon such as toluene, xylene and the like, preferably toluene is used.

7. The process as claimed in claim 1, wherein in step vi) the crude 5-acetyI-3-chloroiminodibenzyl is recrystallized using an organic solvent selected from an alcoholic solvent like methanol, ethanol, n-propanol, iso-propanol and n-butanol, a hydrocarbon solvent like toluene, hexane, heptane, cyclohexane, a halogenated hydrocarbon solvent like methylene chloride, chloroform or combination thereof.
8. The process as claimed in claim 1, wherein in step vi) the crude 5-acetyl-3-chloroiminodibenzyl is recrystallized using single solvent like methanol or combination of two solvents like toluene-hexane or methylene chloride-hexane.

9. The process as claimed in claim 1, wherein in step vii) the alkali metal hydroxide
like potassium hydroxide or sodium hydroxide is used, preferably sodium hydroxide
is used.
10. The process as claimed in claim 1, wherein the amount of n-butanol used in step
vii) with respect to 5-acetyl-3-chloroiminodibenzyl is in the range of 3 to 6 volumes.