Field of the Invention
The present invention relates to an improved process for the preparation of 4,5,7-trichloroquinoline of the formula (I). The 4,5,7-trichloroquinoline of the formula (I) prepared by the process of the present invention is an agrochemical intermediate useful for the preparation of tlingicide.

Consequent to the importance gained for 4,5,7-trichloroquinoline several synthetic processes for its preparation have been reported. For example, Alexander R. Surrey and Henry F. Hammer (J. Am. Chem. Soc, 1245, 1946; US Patent 2,233,970)

describe the process for the preparation of 4,5,7-trichloro quinoline, which involves 5 steps. The reaction is shown in Scheme-I below :

The first step is based on Conrad-Limpach methodology of the reaction of 3,5-dichloroaniline of the formula (5) and ethyl ethoxy acetate (p-ketoester) of the formula (6) in glacial acetic acid to produce corresponding Schiff base of the formula (7). The second step is the ring closure of the formula (7) in medicinal mineral oil at 250 °C to form the quinoline derivative of the formula (8). In the third step of the synthesis the ester was hydrolysed with sodium hydroxide to give hydroxy acid of the formula (9), Subsequently in the fourth step of synthesis, the crude hydroxy acid of the formula (9) was decarboxylated in mineral oil at 270 °C to produce 4-hydroxy-5,7-dichloroquinoiine of the formula (10). 4,5,7-Trichloroquinoline of the formula (1) was finally synthesized by chlorination of the compound of the formula (10) with phosphorous oxy chloride. This process has the following disadvantages

•

The process is a multistep synthesis having in all 5 steps and some steps for example Steps 2 and 4 are tedious and laborious, as the reaction time and work up procedure require more than 24 h.
In the synthesis, ring closure can give a mixture of isomers (as whh m-substituted anilines) as well as a mixture of high melting hydroxy esters of the formula (8), which have to be separated by recrystallisation.
In the synthesis, ring closure reaction step and decarboxylation steps were carried out in medicinal mineral oil at 250 °C which may pose a problem in scale up as performing the reaction and controlling reaction temperature in the range of 250-270 °C needs skill, energy and continuous attention as shooting up of temperature leads to the decomposition of the product.
The reaction masses are very difficult to work up from practical point of view as mineral oil is used as medium which results into highly viscous, greasy masses.
The starting material like ethyl ethoxy acetate is not readily available in this country and has to be procured through imports.

The use of ethoxy methylene maionic ester (EMME) of the formula (11) as an alternative or substitute reagent for ethoxy ethyl acetate in the synthesis is reported by Charles C. Price and Royston M. Roberts (J. Am. Chem. Soc, 68, 1204, 1946). The reaction is shown in Scheme-II below:


This process of preparing 4,5,7-trichloroquinoIine of the formula (1) begins with the reaction reported by Gould and Jacobs where the 3,5-dichloroaniline of the formula (5) was initially reacted with diethyl ethoxy malonate ester of the formula (11) to produce anilino methylene malonate of the formula (12) followed by thermal cyclisation of the formula (12) in Dowtherm A or diphenyl ether to give 4-hydroxy-3-carboxy quinoline derivative of the formula (13). The base hydrolysis of the 4-hydroxy-3-carboxylate gave the 4-hydroxy quinoline-3-carboxylic acid derivative of the formula (14). The thermal decarboxylation of the formula (14) at 250 °C in Dowtherm A or diphenyl ether produces 4-hydroxy-5,7-dichloroquinoline of the formula (10) which finally produces 4,5,7-trichloroquinoline of the formula (1) on chlorination with phosphorous oxychloride.
The original Limpach and Conrad ring cyclization involved heating of Schiff base of the formula (7) in mineral oil at 250-290 °C to produce Quinoline derivative of the formula (8). Gould and Jacobs methodology describes the ring closure of Schiff base of the formula (12) by using superior solvents like diphenyl ether or Dowtherm A as cyclization medium. Still the above referred disadvantages like chances or product decomposition, tedious, laborious work up procedures remain unaddressed even in the

improved synthesis of Gould and Jacob, method of synthesis of 4,5,7-trichloroquinoline of the formula (1).
Considering the wider application of 4,5,7-trichloroquinoline as broad spectrum agrochemical fungicide, we directed our research towards development of an improved process for the preparation of 4,5,7-trichloroquinoline using simple, cheaper and easily available raw materials.
Accordingly, the main objective of the present invention is to provide an improved process for the preparation of 4,5,7-trichloroquinoline, from novel intermediate 3,5-dichloroanilino propionitrile of the formula (2), which is simple and economical.
Another objective of the present is to provide an improved process for the preparation of 4,5,7-trichloroqinoline, which does not require any special skills or continuous attention to process the reaction.
We observed that P-anilino propionitriles have been used as starting materials for the synthesis of, alkyl and alkoxy chloroquinlones in (J. Chem. Soc, Perkin I, 932, 1972). According to this process, the cyanoethylation of various alkyl and alkoxy anilines were carried out with acrylonitrile in acetic acid and it was observed that the reaction takes place via a Michael type of addition to produce the corresponding p-anilino propionitrile. This reagent was not so far been reported for the preparation of trichloroquinolines such as 4,5,7-trichloroquinoline, 4,5,8-trichloroquinoline, 4,6,7-trichloroquinoline. The objectives of the invention have been achieved by preparing a novel intermediate 3,5-dichloroanilino propionitrile according to the method reported above and then converting the said intermediate into 4,5,7-trichloroquinoline of the formula (1). The above said reaction is shown in Scheme-Ill below :


Novel P-anilino propionitrile of the formula (2) can be prepared by reacting 3,5-dichloro aniline of the formula (5) with acrylonitrile of the formula (15) at a temperature in the range of 90 - 130 °C for a period in the range of 4-16 h in the presence of cupric salts to yield novel 3,5-dichloroanilino propionitrile of the formula (2). The reaction may be carried out at a temperature in the range of 100 -110 °C for a duration of in the range of 6 -8h.
Accordingly, the present invention provides an improved process for the preparation of 4,5,7-trichloro quinoline of the formula (1), which comprises :
(i). reacting 3,5-dichlord aniline of the formula (5) with acrylonitrile of the formula
(15 ) at a temperature in the range of 90 - 130 °C for a period in the range of 4-16 h in
the presence of cuppric salts to yield novel 3,5-dichloroanilino propionitrile of the
formula (2),
(ii). hydrolysing the 3,5-dichloroanilino propionitrile of the formula (2) by known
methods to form 3,5-dichloroanilino propionic acid of the formula (16),
(iii). cyclysing the 3,5-dichloroanilino propionic acid of the formula (16) by known
methods to yield compound of formula (17),

(iv). ' dehydrogenating the compound of formula (17) by known methods to yield 4-
hydroxy-5,7-dichloro quinoline of the formula (10),
(v). chlorinating the compound of formula (10) by known methods to yield 4,5,7-
trichloroquinoline of the formula (1) and
(vi). recovering the 4,5,7-trichloroquinolineof the formula (1) by conventional
methods.
Cuppric salt which may be employed for the cyanoethylation of 3,5-dichloroaniline (3,5-DCA) with acrylonitrile may be selected from copper (1) chloride, cuppric acetate and the cyanoethylation can be carried out at a temperature preferably at 100-110 °C. The reaction period preferably may range from 6-8 h. In situ hydrolysis of the nitrile of the formula (2) using 10 % aqueous base such as NaOH, KOH, K2CO3, Na2C03 or with dil. hydrochloric acid yielded the corresponding (3-anilino propionic acid of the formula (16). 10% sodium hydroxide was found to be more effective among all the bases employed. Cyclization of the propionic acid of the formula (16) may be preferably carried out with 30% sulphuric acid, orthophosphoric acid, phosphorous pentoxide, phosphorous oxychloride, thionyl chloride, poly phosphoric acid (PPA), preferably PPA in the temperature range of 60-120 °C, preferably at 80-100 °C. The reaction period ranges from 4-14 h, preferably in 6-8 h, optimal yields of 2,3-dihydroquinoline-4(lH)-one of the formula (17) were observed. The aromatization of the dihydroquinoline of the formula (17) was carried out using 5% Pd-C in high boiling organic solvents like diglyme, 0-dichlorobenzene, ethylene glycol, dimethyl acetamide or diphenyl ether, preferably in diphenyl ether in temperature range of 160-260 °C preferably in the temperature of 180-200 °C. The reaction was carried out in 8-18 h, preferably for 10-12 h. In the subsequent chlorination step the 4-hydroxy-5,7-dichloroquinoline of the formula (10) was reacted with phosphorous oxychloride at 130-140 °C temperature in about 1 h to produce the final 4,5,7-trichloroquinoline of the formula (1) in optimal yields.
In a similar manner, the process can also be applied for the preparation of other trichloroquinolines.

,The present invention is described in detail in the examples given below which are provided by way of illustration only and therefore should not be construed to limit the scope of the invention.
Example 1 : Preparation of 3,5-dichioroanilino P-propionitrile of the formula (2)
162 g of 3,5-dichloroaniline, 53 g of acrylonitrile and 10.2 g of cupric acetate monohydrate was taken into 1 L 4 necked round bottom flask fitted with a mechanical stirrer. The reaction mass was stirred and heated to 80-90 °C for a period of 6-8 h monitoring the reaction by TLC. The resulting dark mixture was quenched with 200 ml NH4OH solution till the pH reaches 8-8.5. Extract the basic aqueous layer with toluene (3 X 1 L) followed by water washing ( 3 x 200 ml). Concentrate the toluene layer on rotavapor at 60-70 °C / 150-170 mm vacuum till no more drops of toluene are observed. The crude 3,5-dichloroanilino propionitrile was distilled and the vapours at b.p. 139-141 °C / 0.3 mm was collected as colorless, somewhat viscous liquid was the novel pure 3,5-dichloroanilino-p-propionitrile of the formula (2), (Wt. 150 g, Y : 70 %, mp 76-78 °C).
The IR spectrum as KBr shows the following absorption bands at 3470 cm'' (-NH stretch), 2250 cm'' (-CsN stretch). The 'H NMR spectrum in CDCI3 (TMS internal standard) shows the following signals at 5 2.5 (t, 3H, -CH2-C=N-), 3.4 (t, 3H, -NH-CH2-CH2), 4.3 (broad singlet, IH, -NH-), 6.7-7.2 (m, 3H, aromatic)
Example 2 :
Step (i): Preparation of 3,5-dichloro P-anilino propionic acid of the formula (16)
214 g of 3,5-dichloro P-anilino propiontrile prepared by the process described in example 1 above and 800 ml of 10 % sodium hydroxide were taken into 2 L four necked round bottom flask fitted with a mechanical stirrer and condenser. The reaction mass was heated to 90-95 °C for a period of 8-10 h till there was no further evolution of ammonia in the reaction. The mixture was cooled and acidified with cone. Hydrochloride acid (~ 200 ml) for pH of 5.8-6.0 and extracted with toluene (500 ml x 4). The toluene extracts

were clubbed and washed with water (500 ml x 2). The organic toluene layer was concentrated on water bath at 60-70 °C under vacuum of 150-200 mm to a volume of 300-400 cc and the precipitated 3,5-dichloro P-anilino propionic acid was filtered and dried at 50-60 °C in the oven. The dried product namely 3,5-dichloro-P-anilino propionic acid of the formula (16) appears as light yellow crystalline solid, weighs about 220 g, (Y : 94.4%, m.p. 102-104 °C). The IR spectrum as KBr shows the following absorption bands at 3470 cm"' (-NH stretch), 1720 cm"' (-C=0, stretch in -COOH). The 'H NMR spectrum in CDCI3 (TMS internal standard) shows the following signals at 2.5-3.6 (t, 2H, -CH2-COOH), 3.2-3.4 (t, 2H, -NH-CH2-CH2-), 5.0 (broad singlet, IH, -COOH), 6.5-7,4 (m, 3H, aromatic).
Step (ii) : Preparation of 5,7-dichloro-2,3-dihydroquinoline-4(lH)-one of the formula (17)
400 g of phosphorous pentoxide, 130 ml of orthophosphoric acid were taken into 2 L four necked round bottom flask, fitted with a mechanical stirrer and condenser. The mixture was heated to 100 °C for 2 h. 233 g of 3,5-dichloro P-anilino propionic acid of the formula (16) prepared by the process described in step (i) above was added slowly at 60-70 "C in about 30 min. and the reaction mass was maintained at 90-100 °C for further 2 h after addition is completed. The reaction mass was brought to room temperature after TLC monitoring and chilled water (1 L) was added to the reaction mixture and the solid separated was extracted with toluene (500 ml x 3). The organic toluene layer was washed with water and concentrated on a water bath at 60-70 °C under a vacuum of 150-200 mm to a volume of 200-300 ml. The precipitated 5,7-dichloro-2,3-dihydro quinoline-4(lH)-one of the formula (17) was filtered, dried in oven at 60-70 °C. The product appears as light yellow solid (weight about 160 g) (Y : 74 %, m.p. 184-86 °C, purity 98% by HPLC). The IR spectrum as KBr shows the following absorption bands at 3470 cm"' (-NH- stretch), 1720 cm"' (-CO stretch). The 'H NMR spectrum in CDCI3 shows the following signals at 5 2.8 (m, 2H, -CH2-CO-), 3.63 (m, 2H, -NH-CH2-), 6.3 (s, IH, aromatic at 8*), 7.1 (s, IH, aromatic 6"').

Step (iii): Preparation of 5,7-dichloro-4-hydroxy quinoline of the formula (10)
215 g of 5,7-dichloro-2,3-dihydroquinoline-4(lH)-one of the formula (17) prepared according to the process described in step (ii) above, 32 g of 5% Pd/C, 500 ml of diphenyl ether were taken into four necked round bottomed flask, fitted with a mechanical stirrer and reflux condenser. The reaction mixture was stirred and heated to 180-200 °C for 12-14 h monitoring the reaction by TLC. The reaction mass was brought to room temperature and the precipitated solid 5,7-dichloro-4-hydroxy quinoline of the formula (10) was filtered and dried. The product 5,7-dichloro-4-hydroxy quinoline of the formula (10) and 5 % Pd/C both are insoluble in the diphenyl ether medium employed, the product is contaminated with Palladium and charcoal. The product 5,7-dichloro-4-hydroxy quinoline of the formula (10) was extracted with 10 % methanolic NaOH (~ 400 ml) and the insoluble 5 % Pd/C was filtered and dried. The extracted methanolic sodium hydroxide layer was neutralized with Cone. HCl (-100 ml) till the pH reaches 5.8-6.0. The precipitated pure 5,7-dichloro-4-hydroxy quinoline of the formula (6) was filtered, dried in the oven at 60-70 °C till the MC reaches < 0.5 %. The product 5,7-dichloro-4-hydroxy quinoline (10) appears as off white crystalline solid, weights about 138 g (Y : 65 %, m.p. 345-48 °C, purity 97-98 % by HPLC). The ER (KBr) spectrum shows the following absorption bands at 3450 cm'' (-0H stretch). The 'H NMR spectrum could not be recorded because of its poor solubility in any of the dueterated organic solvents.
Step (iv): Preparation of 4,5,7-trichloroquinoline of the formula (1)
213 g of 5,7-dichloro-4-hydroxy quinoline of the formula (10) prepared according to the process described in step (iii) above, 1 L of toluene, 102 ml of phosphorous oxychloride were taken into 1 L four necked round bottom flask fitted with a mechanical stirrer and reflux condenser. The reaction mixture was stirred and heated to 120-130 °C for reflux and maintained at 120-130 °C temperature for one hour, monitoring the reaction by TLC. The reaction mixture was brought to room temperature, the toluene layer was washed with water (300 ml x 3) till the pH reaches to 6-7. The toluene layer was decolorised

with charcoal. Concentrated on water bath at 60-70 °C / 150-200 mm to a minimal volume of 100-200 ml toluene and cooled to 5-10 °C. The precipitated 4,5,7-trichloro quinoline of the formula (1) was filtered and dried at 50 °C and the dried product appears as off white crystalline solid, weighs about 208 g (Y = 90 %, m.p. 104 °C, purity 98-99 % by HPLC). The 'H NMR spectrum in CDCb (TMS as internal standard) shows the following signals at 5 7.51 (d, IH, aromatic proton at C-3), 7.63 (d, IH, aromatic proton at C-6), 8.03 (d, IH, aromatic proton at C-8), 8.67 (d, IH, aromatic proton at C-2).
Example 3 : Preparation of 4,5,7-trichloro quinoline of the formula (1)
Step (i) : One pot synthesis of 3,5-dichloro-P-anilino propionic acid of the formula
(16)
162 g of 3,5-dichloro aniline, 53 g of acrylonitrile and 10.2 g cupric acetate monohydrate were taken into 2 L four necked round bottomed flask fitted with a mechanical stirrer and reflux condenser. The reaction mass was stirred and heated to 80-90 °C for a period of 6-8 h, monitoring the reaction by TLC, 800 ml of 10 % aqueous sodium hydroxide was added at 50-60 °C temperature in about 30 min. and further the reaction mixture was heated to 90-100 °C for a period of 8-10 h, fill there was not further evolution of ammonia in the reacfion. The mixture was cooled and acidified with cone. HCl (~ 200 ml) to pH 5.8-6.0 and extracted with toluene (500 ml x 4). The toluene extracts are clubbed and washed with water (500 ml x 2). The organic toluene layer was concentrated on water batch at 300-400 cc and the precipitated 3,5-dichloro-P-anilino propionic acid of the formula (16) was filtered and dried at 50-60 °C in the oven. The dried 3,5-dichloro-P-anilino propionic acid of the formula (16) appears as light yellow crystalline solid, weighs about 150 g (Y : 64 %, m.p. 102-104 °C).
Step (ii) : Preparation of 5,7-dichloro-2,3-dihydroquinoline-4(lH)-one of the formula (17)
400 g of phosphorous pentoxide and 130 ml of orthophosphoric acid were taken into 2 L four necked round bottom flask, fitted with a mechanical stirrer and condenser. The

mixture was heated to 100°C for 2 h. 233 g of 3,5-dichloro-P-anilino propionic acid of the formula (16) prepared by the process described in step (i) above was added slowly at 60-70 °C in about 30 min. and the reaction mass was maintained at 90-100 °C for ftirther 2 h after addition is completed. The reaction mass was brought to room temperature after TLC monitoring and chilled water (I L) was added to the reaction mixture and the solid reported was extracted with toluene (500 ml x 3). The organic toluene layer was washed with water and concentrated on a water bath at 60-70 °C under a vacuum of 150-200 mm to a volume of 200-300 ml. The precipitated 5,7-dichloro-2,3-dihydro quinoline-4(lH)-one of the formula (17) was filtered, dried in oven at 60-70 °C. The product appears as light yellow solid (weight about 160 g) (Y : 74 %, m.p, 184-86 °C, purity 98 % by HPLC). The IR spectrum as KBr shows the following absorption bands at 3470 cm"' (-NH- stretch), 1720 cm'' (-CO stretch). The 'H NMR spectrum in CDCI3 shows the following signals at 5 2.8 (m, 2H, -CH2-CO-), 3.63 (m, 2H, -NH-CH2-), 6.3 (s, IH, aromatic at s\ 7.1 (s, IH, aromatic 6*).
Step (Hi): Preparation of 5,7-dichloro-4-hydroxy quinoline of the formula (10)
215 g of 5,7-dichloro-2,3-dihydroquinoline-4(lH)-one of the formula (17) prepared according to the process described in step (ii) above and 32 g of 5 % Pd/C, 500 ml of diphenyl ether were taken into four necked round bottomed flask, fitted with a mechanical stirrer and reflux condenser. The reaction mixture was stirred and heated to 180-200 °C for 12-14 h monitoring the reaction by TLC. The reaction mass was brought to room temperature and the precipitated solid 5,7-dichloro-4-hydroxy quinoline of the formula (10) was filtered and dried. The product 5,7-dichloro-4-hydroxy quinoline of the formula (10) and 5 % Pd/C both are insoluble in the diphenyl ether medium employed, the product is contaminated with Palladium and charcoal. The product 5,7-dichloro-4-hydroxy quinoline of the formula (10) was extracted with 10 % methanolic NaOH (~ 400 ml) and the insoluble 5 % Pd/C was filtered and dried. The extracted methanolic sodium hydroxide layer was neutralized with cone. HCl (-100 ml) till the pH reaches 5.8-6.0. The precipitated pure 5,7-dichloro-4-hydroxy quinoline of the formula (10) was filtered, dried in the oven at 60-70 °C till the MC reaches < 0.5 %. The product 5,7-dichloro-4-

hydroxy quinoline of the formula (10) appears as off white crystalline solid, weighs about 138 g,(Y : 65 %, m.p. 345-48 °C purity 97-98 % by HPLC). The IR (KBr) spectrum shows the following absorption bands at 3450 cm'' (-0H stretch). The 'H NMR spectrum could not be recorded because of its poor solubility in any of the deuterated organic solvents.
Step (iv): Preparation of 4,5,7-trichloroquinoline of the formula (1)
213 g of 5,7-dichloro-4-hydroxy quinoline of the formula (10) prepared according to the process described in step (iii) above, 1 L of toluene and 102 ml of phosphorous oxychloride were taken into 1 L four necked round bottom tlask fitted with a mechanical stirrer and reflux condenser. The reaction mixture was stirred and heated to 120-130 °C for reflux and maintained at 120-130 °C temperature for one hour, monitoring the reaction by TLC. The reaction mixture was brought to room temperature, the toluene layer was washed with water (300 ml x 3) till the pH reaches to 6-7. The toluene layer was decolorised with charcoal. Concentrated on water bath at 60-70 °C / 150-200 mm to a minimal volume of 100-200 ml toluene and cooled to 5-10 °C. The precipitated 4,5,7-trichloro quinoline of the formula (1) was filtered and dried at 50 °C and the dried product appears as off white crystalline solid, weighs about 208 g (Y = 90 %, m.p. 104 °C, purity 98-99 % by HPLC). The 'H NMR spectrum in CDCI3 (TMS as internal standard) shows the following signals at 5 7.51 (d, IH, aromatic proton at C-3), 7.63 (d, IH, aromatic proton at C-6), 8.03 (d, IH, aromatic proton at C-8), 8.67 (d, IH, aromatic proton at C-2).
Advantages of the present invention :
An important advantage is the use of inexpensive, readily available reagents such as acrylonitrile in place of expensive, not readily available reagents such as ethyl ethoxy acetate, ethoxy methylene malonic ester (EMME) as used in the synthesis in prior art.

Another advantage is the simplification of the process. The cyclisation of P-anilino propionic acid step is carried out using PPA at comparatively lower temperature (100-110 °C), where as the ring closure reaction step is carried out in mineral oil, Dowtherm A or diphenyl ether at very high temperature of 250-270 °C in the prior art, where there is a risk of product decomposition.
Another advantage is the total elimination of decarboxylation step, which is again risky and performed at very high temperature range of 250-270 °C, where any temperature shoot up leads to product decomposition.
Another advantage is the simplification of work up procedure as nowhere paraffin oil is used for ring closure or aromatisation which makes the process cost effective, simple and commercially viable.
Another advantage is the possibility of one pot synthesis of 3,5-dichloro P-anilino propionic acid of the formula (13) from 3,5-dichloro aniline without isolation of the novel intermediate P-anilino propionitrile of the formula (II) without compromising the effective yield and purity of the final compound namely 4,5,7-trichloro quinoline.

We claim :
1. An improved process for the preparation of 4,5,7-trichloro quinoiine of tiie
formula (1),

which comprises :
(i). reacting 3,5-dichloro aniline of the formula (5)

with acrylonitrile of the formula (12)

at a temperature in the range of 90 - 130 °C for a period in the range of 4-16 h in the presence of cuppric salts to yield novel 3,5-dichloroanilino propionitrile of the formula
(2),
(ii). hydrolysing the 3,5-dichloroanilino propionitrile of the formula (2) by known methods to form 3,5-dichloroanilino propionic acid of the formula (16),

(iii). cyclysing the 3,5-dichloroanilino propionic acid of the formula (16) by known methods to a compound of formula (17),


, (iv). dehydrogenating the compound of fonnula (17) by known methods to yield 4-hydr6xy-5,7-dichloro quinoHne of the formula (10)

(v). chlorinating the compound of formula (10) by known methods to yield 4,5,7-
trichloroquinoline of the formula (1) and
(vi). recovering the 4,5,7-trichloroquinoline of the formula (1) by conventional
methods.
2 The process as claimed in claim 1, wherein the reaction in step (i) is carried out at
a temperature in the range of 100 -110 °C.
3. The process as claimed in claims 1 and 2, wherein the duration of reaction in step (i) ranges from 6 - 8 h.
4. The process as claimed in claims 1 to 3, wherein the hydrolysis in step (ii) is effected using 10 % aqueous base such as NaOH, KOH, Na2C03, K2CO3 or dil. HCl.
5. The process as claimed in claims 1 to 4, wherein the cyclisation is carried out employing 30 % sulphuric acid, orthophosphoric acid, phosphorous pentoxide, phosphorous oxychloride, thionyl chloride, poly phosphoric acid (PPA).
6. The process as claimed in claims 1 to 5 wherein the temperature for the reaction
in step (iii) ranges from 80-100 °C.
7. The process as claimed in claims 1 to 6, wherein the duration of the reaction in step (iii) ranges from 6-8 h.
8. The process as claimed in claims 1 to 7, wherein the dehydrogenation in step (iv) is carried out using 5 % Pd-C in high boiling organic solvents like diglyme, o-dichlorobenzene, ethylene glycol, dimethyl acetamide or diphenyl ether.
9. The process as claimed in claims 1 to 8, wherein the reaction in step (iv) is carried out at a temperature in the range of 160 - 260°C, preferably from 160-180 °C.
10. The process as claimed in claims 1 to 9, wherein the duration of the reaction in step (iv) ranges from 10-12 h.
11. The process as claimed in claims 1 to 10, wherein the chlorination in step (v) is carried out using phosphorous oxychloride.

12. The process as claimed in claims 1 to 11, wherein the reaction in step (v) is carried out at a temperature in the range of 130-140 °C.
13. A process for the preparation of 4,5,7-trichloroquinoline substantially as herein described with reference to examples 2 & 3.