DESC:FIELD
The present disclosure relates to a process for preparing 4-(4-aminophenyl)morpholin-3-one.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
4-(4-aminophenyl)morpholin-3-one (I) (CAS number: 438056-69-0) is an intermediate used for preparing Rivaroxaban, an anti-coagulant drug.
Conventionally, the preparation of 4-(4-aminophenyl)morpholin-3-one (I) involves nitration of 4-phenylmorpholin-3-one followed by reduction using palladium catalyst. Nitration uses corrosive reagents such as sulphuric acid and nitric acid. In addition, the nitration reaction involves vigorous reaction conditions and produces impurities. The reduction involves the use of a palladium catalyst, an expensive metal, as a reducing agent which increases the overall operational cost of the process.
Therefore, there is felt a need for a simple, and economic process for preparing 4-(4-aminophenyl)morpholin-3-one (I) that mitigates the aforestated drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for preparing of 4-(4-aminophenyl)morpholin-3-one which is simple, and economic.
Yet another object of the present disclosure is to provide a process for preparing of 4-(4-aminophenyl)morpholin-3-one with high purity.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides to a process for preparing 4-(4-aminophenyl)morpholin-3-one (I).
The process comprises chlorinating 2-(2-chloroethoxy)acetic acid (II) using a chlorinating agent in a first fluid medium to obtain 2-(2-chloroethoxy)acetyl chloride (III). 2-(2-chloroethoxy)acetyl chloride (III) is then condensed with 4-nitroaniline (IV) in a second fluid medium, and in the presence of a first base to obtain 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V). 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) is cyclized in the presence of a phase transfer catalyst and a second base to obtain 4-(4-nitrophenyl)morpholin-3-one (VI). 4-(4-nitrophenyl)morpholin-3-one (VI) is reduced using a reducing agent in a third fluid medium, followed by purification to obtain 4-(4-aminophenyl)morpholin-3-one (I) having purity greater than 99%.
DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
The present disclosure envisages a simple, and economic process for preparing 4-(4-aminophenyl)morpholin-3-one (I) having purity greater than 99%, which is represented as

The schematic representation of the process of the present disclosure is given below:

The process for preparing 4-(4-aminophenyl)morpholin-3-one (I) in accordance with the present disclosure is described in detail herein below:
Step 1: Chlorination of 2-(2-chloroethoxy)acetic acid (II)
In first step, 2-(2-chloroethoxy)acetic acid (II) is chlorinated using a chlorinating agent in a first fluid medium at a temperature in the range of 40 to 65 °C to obtain 2-(2-chloroethoxy)acetyl chloride (III).

The chlorination step is described in detail herein below.
A reactor is charged with a first fluid medium and 2-(2-chloroethoxy)acetic acid (II) to a temperature in the range of 40 to 65 °C to obtain a first reaction mixture. A chlorinating agent is added to the first reaction mixture and stirred for 4 to 6 hours. After completion of the reaction (monitored by TLC), excess chlorinating agent is removed by vacuum distillation to obtain a first resultant mixture comprising a solution of 2-(2-chloroethoxy)acetyl chloride (III) in a first fluid medium. The first resultant mixture so obtained can be used directly in the next step without further purification.
The chlorinating agent is selected from the group consisting of thionyl chloride, oxalyl chloride, methanesulfonyl chloride and trichloromethanesulfonyl chloride. The mole ratio of 2-(2-chloroethoxy)acetic acid (II) to the chlorinating agent is in the range of 1:1 to 1: 5.
In an exemplary embodiment of the present disclosure, the chlorinating agent is thionyl chloride and the mole ratio of 2-(2-chloroethoxy)acetic acid (II) to thionyl chloride is 1: 1.16.
The first fluid medium is selected from the group consisting of chlorobenzene, benzene and toluene. In an exemplary embodiment of the present disclosure, the first fluid medium is chlorobenzene.
Step 2: Condensation of 2-(2-chloroethoxy)acetyl chloride (III)
In second step, 2-(2-chloroethoxy)acetyl chloride (III) is condensed with 4-nitroaniline (IV) in a second fluid medium, in the presence of a first base at a temperature in the range of 15 to 40 °C to obtain 2-(2-chloroethoxy)-n-(4-nitrophenyl)acetamide (V).

The condensation step is described in detail herein below.
A reactor is charged with a second fluid medium and p-nitroaniline (IV) and cooled to a temperature in the range of 10 to 15 °C, followed by addition of a solution of soda ash (sodium carbonate + demineralized water) to obtain a second reaction mixture. The first resultant mixture comprising 2-(2-chloroethoxy)acetyl chloride (III) obtained in the Step 1 is added in drop-wise manner to the second reaction mixture over a period of 4 to 6 hours, and then stirred for a period of 5 to 8 hours. After completion of the reaction (monitored by TLC), demineralized water is added to obtain a biphasic mixture comprising an aqueous layer and an organic layer. The organic layer is separated from the biphasic mixture. The separated organic layer is washed with aqueous hydrochloric acid, followed by washing with demineralized water to obtain a second resultant mixture comprising a solution of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) in a second fluid medium. The second resultant mixture can be used directly in the next step without further purification.
The mole ratio of 2-(2-chloroethoxy)acetyl chloride (III) to 4-nitroaniline (IV) is in the range of 1:0.5 to 1:1. In an exemplary embodiment of the present disclosure, the mole ratio of 2-(2-chloroethoxy)acetyl chloride (III) to 4-nitroaniline (IV) is 1:0.75.
The first base is selected from the group consisting of sodium carbonate, potassium carbonate and caesium carbonate. The mole ratio of 2-(2-chloroethoxy)acetyl chloride (III) to the first base is in the range of 1: 0.5 to 1:1.
During the reaction of 4-nitroaniline and 2-(2-chloroethoxy)acetyl chloride, hydrogen chloride (HCl) gas is generated which is neutralized with the base. If base is not added in the reaction then hydrogen chloride gas forms salt with 4-nitroaniline which affects the yield and the quality of the product.
In an exemplary embodiment of the present disclosure, the first base is sodium carbonate and the mole ratio of 2-(2-chloroethoxy)acetyl chloride (III) to sodium carbonate is 1: 0.8.
The second fluid medium is selected from the group consisting of methylene dichloride, carbon tetrachloride, ether, and alcohol. In one embodiment, the second fluid medium is methylene dichloride.

Step 3: Cyclization of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V)
In third step, 2-(2-chloroethoxy)-n-(4-nitrophenyl)acetamide (V) obtained in Step 2 is cyclized in the presence of a phase transfer catalyst, using a second base at a temperature in the range of 10 to 30 °C to obtain 4-(4-nitrophenyl)morpholin-3-one (VI).

The step of cyclization is described in detail herein below.
A phase transfer catalyst is added to the second resultant mixture comprising 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) at a temperature in the range of 20 to 30 °C to obtain a third reaction mixture. Aqueous solution of the second base is added to the third reaction mixture over a period of 2 to 3 hours and stirred for 6 to 8 hours. After completion of the reaction (monitored by TLC), demineralized water is added to obtain a biphasic mixture comprising an aqueous layer and an organic layer. The organic layer is separated from the biphasic mixture and washed with demineralized water. The washed organic layer is then subjected to vacuum distillation to remove the first fluid medium and the second fluid medium to obtain a residue. Iso-propyl alcohol is added to the residue and stirred at a temperature in the range of 0 to 5°C for a period of 1 to 2 hours to obtain slurry. The so obtained slurry is filtered to obtain solid. The solid is separated and washed with iso-propyl alcohol, followed by drying to obtain 4-(4-nitrophenyl)morpholin-3-one (VI) having purity of 99 %.
The phase transfer catalyst is selected from tetra-n-butylammonium bromide, and crown ether. The mole ratio of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) to the phase transfer catalyst is in the range of 1: 0.01 to 1: 0.1.
In an exemplary embodiment of the present disclosure, the phase transfer catalyst is tetra-n-butylammonium bromide and the mole ratio of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) to tetra-n-butylammonium bromide is 1: 0.03.
The second base is selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and triethyl amine. The mole ratio of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) to the second base is in the range of 1: 1 to 1: 3.
In an exemplary embodiment of the present disclosure, the second base is an aqueous solution of sodium hydroxide. Sodium hydroxide solution is prepared by adding sodium hydroxide in demineralized water.
Step 4: Reduction of 4-(4-nitrophenyl)morpholin-3-one (VI)
4-(4-nitrophenyl)morpholin-3-one (VI) so obtained in Step 3 is reduced using a reducing agent in a third fluid medium at a temperature in the range of 50 to 80 °C to obtain crude 4-(4-aminophenyl)morpholin-3-one (I).

The step of reduction is described in detail herein below.
An autoclave is charged with a third fluid medium, 4-(4-nitrophenyl)morpholin-3-one (VI) obtained in step III, and a reducing agent to obtain a fourth reaction mixture. The autoclave is locked and flushed twice with nitrogen and twice with hydrogen. The hydrogen pressure of the autoclave is maintained at 6 to 7 kg/cm2 at 60 to 65 °C. The reaction mixture is stirred for a time period in the range of 8 to 10 hours. After completion of the reaction (monitored by TLC), the temperature is reduced to 50 to 40 °C, and hydrogen pressure is released to obtain a fourth resultant mixture comprising crude 4-(4-aminophenyl)morpholin-3-one (I).
The so obtained fourth resultant mixture is filtered to obtain a filtrate comprising crude 4-(4-aminophenyl)morpholin-3-one (I). Aqueous hydrochloric acid is added in drop-wise manner to the filtrate, followed by cooling to 5 to 10 °C. A solid is precipitated, which is separated by filtration to obtain a residue. Demineralized water is then added to the so obtained residue, followed by addition of aqueous sodium hydroxide in drop-wise manner to obtain slurry. The slurry is cooled to a temperature in the range of 5 to 10 °C and maintained for a period of 2 to 3 hours, followed by filtration and drying to obtain 4-(4-aminophenyl)morpholin-3-one (I) having purity greater than 99%.
In an embodiment of the present disclosure, the reducing agent is Raney nickel. Raney nickel is economical and acts as a strong reducing agent. The weight ratio of 4-(4-nitrophenyl)morpholin-3-one (VI) to the reducing agent is in the range of 1: 0.01 to 1: 0.1, preferably 1: 0.05.
It is evident from the above reaction steps that the process of the present disclosure employs mild reaction conditions, and uses readily available reagents that are economical. Also, the process of the present disclosure produces 4-(4-aminophenyl)morpholin-3-one (I) with high purity. Therefore, the process of the present disclosure to prepare 4-(4-aminophenyl)morpholin-3-one (I) is simple, and economical.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Experiment 1: A process for the preparation of 4-(4-aminophenyl)morpholin-3-one (I)
Experiment 1A: Step 1- Preparation of 2-(2-chloroethoxy)acetyl chloride (III) from 2-(2-chloroethoxy)acetic acid (II)
A reactor was charged with chlorobenzene (2400 L) and 2-(2-chloroethoxy)acetic acid (II) (800 g) at 30 °C, and heated to 50 °C to obtain a first reaction mixture. Thionyl chloride (800 g) was added to the first reaction mixture at 50 °C and stirred for 4 hours at 50 °C to obtain a first resultant mixture. After completion of the reaction (monitored by TLC), excess thionyl chloride was removed from the first resultant mixture by vacuum distillation to obtain 2-(2-chloroethoxy)acetyl chloride (III).
Experiment 1B: Step 2- Preparation of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) from 2-chloroethoxyacetyl chloride (III)
A reactor was charged with methylene dichloride (6000 ml) and p-nitroaniline (IV) (600 g), and cooled to 15 °C. solution of soda ash (502 g of sodium carbonate + 1000 ml of demineralized water) was added at 15 °C to obtain a second reaction mixture. The first resultant mixture obtained in experiment 1a, comprising 2-(2-chloroethoxy)acetyl chloride (III) was added in drop-wise manner to the second reaction mixture over a period of 4 hours, followed by stirring for 5 hours. After completion of the reaction (monitored by TLC), demineralized water (500 ml) was added to obtain a biphasic mixture comprising an aqueous layer and an organic layer. The organic layer was separated from the biphasic mixture. The separated organic layer was washed with aqueous hydrochloric acid (250 mL), followed by washing with demineralized water (250 mL) to obtain a second resultant mixture comprising a solution of 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) in a second fluid medium. The second resultant mixture is used directly in the next step without further purification.
Experiment 1C: Step 3- Preparation of 4-(4-nitrophenyl)morpholin-3-one (VI) from 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V)
Tetra-n-butylammonium bromide (60 g) was added to the second resultant mixture obtained in experiment 1b, comprising 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) at 20 °C to obtain a third reaction mixture. A solution of sodium hydroxide (265 g of sodium hydroxide + 1050 ml of demineralized water) was added to the third reaction mixture over a period of 2 hours and stirred for 6 hours. After completion of the reaction (monitored by TLC), demineralized water (7000 ml) was added to obtain a biphasic mixture comprising an aqueous layer and an organic layer. The organic layer was then separated and washed with demineralized water (500 ml). The washed organic layer was then subjected to vacuum distillation to remove methylene dichloride at 45 °C and chlorobenzene at 60 °C to obtain a residue. Isopropyl alcohol (850 ml) was added to the residue and stirred at 0 °C for 1 hour 4-(4-nitrophenyl)morpholin-3-one (VI) at 25 °C for 1 hour, followed by cooling at to obtain slurry. Filtering the slurry and washing the solid obtained with cooled isopropyl alcohol (50 ml) to obtain 4-(4-nitrophenyl)morpholin-3-one (VI) with purity of 99 %.
Experiment 1D: Step 4- Preparation of 4-(4-aminophenyl)morpholin-3-one (I) from 4-(4-nitrophenyl)morpholin-3-one (VI)
An autoclave was charged with dimethylformamide (2000 ml), 4-(4-nitrophenyl)morpholin-3-one (VI) (1000 g) obtained in experiment 1c, and Raney nickel (50 g) at 25 °C to obtain a fourth reaction mixture. The autoclave was locked and flushed twice with nitrogen and twice with hydrogen at 25 °C. The hydrogen pressure of the autoclave was maintained at 6 kg/cm2 at 60 °C. The fourth reaction mixture was stirred for 8 hours. After completion of reaction (monitored by TLC), the temperature was reduced to 50 °C and hydrogen pressure was released to obtain a fourth resultant mixture comprising crude 4-(4-aminophenyl)morpholin-3-one (I).
Further, the fourth resultant mixture was flushed with nitrogen and filtered to obtain a filtrate. Concentrated hydrochloric acid (750 mL) was added to the filtrate and the filtrate was stirred at 5 °C for 1 hour. The solid was precipitated, which is separated by filtration to obtain a residue. Demineralized water (3000 ml) was then added to the so obtained residue, followed by addition of aqueous sodium hydroxide (235 g of sodium hydroxide + 250 ml of demineralized water) in drop-wise manner to obtain slurry. The slurry is cooled to 5 °C and to obtain a cooled mixture. The cooled mixture was filtered and washed with demineralized water (500 ml), followed by drying at 60 °C to obtain 700 g of 4-(4-aminophenyl)morpholin-3-one (I) having HPLC purity of 99.5 %.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for the preparation of 4-(4-aminophenyl)morpholin-3-one:
? that is simple, and economical; and
? with purity greater than 99 %.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation
,CLAIMS:WE CLAIM:
1. A process for preparing 4-(4-aminophenyl)morpholin-3-one (I), said process comprising:
i. chlorinating 2-(2-chloroethoxy)acetic acid (II) using a chlorinating agent in a first fluid medium to obtain 2-(2-chloroethoxy)acetyl chloride (III);
ii. condensing said 2-(2-chloroethoxy)acetyl chloride (III) with 4-nitroaniline (IV) in a second fluid medium, and in the presence of a first base to obtain 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V);
iii. cyclizing said 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) in the presence of a phase transfer catalyst and a second base to obtain 4-(4-nitrophenyl)morpholin-3-one (VI); and
iv. reducing said 4-(4-nitrophenyl)morpholin-3-one (VI) using a reducing agent in a third fluid medium, followed by purification to obtain 4-(4-aminophenyl)morpholin-3-one (I) having purity greater than 99%.
2. The process as claimed in claim 1, wherein
• the step (i) of chlorination is carried at a temperature in the range of 40°C to 65°C;
• the step (ii) of condensation is carried at a temperature in the range of 15°C to 40°C;
• the step (iii) of cyclization is carried at a temperature in the range of 10°C to 30°C; and
• the step (iv) of reduction is carried at a temperature in the range of 50°C to 80°C.
3. The process as claimed in claim 1, wherein purification of 4-(4-aminophenyl)morpholin-3-one (I) involves following steps:
a. adding hydrochloric acid in drop-wise manner at a temperature in the range of 5°C to 10°C, followed by stirring to obtain a suspension comprising a solid phase and a liquid phase, filtering said suspension to obtain a residue;
b. adding aqueous solution of sodium hydroxide to said residue in drop-wise manner at a temperature in the range of 5°C to 10°C and stirring, followed by filtration and drying to obtain 4-(4-aminophenyl)morpholin-3-one (I) having purity greater than 99%.
4. The process as claimed in claim 1, wherein said chlorinating agent is selected from the group consisting of thionyl chloride, oxalyl chloride, methanesulfonyl chloride and trichloromethanesulfonyl chloride.
5. The process as claimed in claim 1, wherein the mole ratio of said 2-(2-chloroethoxy)acetic acid (II) to said chlorinating agent is in the range of 1:1 to 1: 5.
6. The process as claimed in claim 1, wherein said first fluid medium, said second fluid medium and said third fluid medium are independently selected from the group consisting of chlorobenzene, benzene, toluene methylene dichloride, carbon tetrachloride, ether, dimethyl formamide and alcohol.
7. The process as claimed in claim 1, wherein said first base is selected from the group consisting of sodium carbonate, potassium carbonate and caesium carbonate.
8. The process as claimed in claim 1, wherein the mole ratio of said 2-(2-chloroethoxy)acetyl chloride (III) to said first base is in the range of 1: 0.5 to 1:1.
9. The process as claimed in claim 1, wherein the mole ratio of said 2-(2-chloroethoxy)acetyl chloride (III) to said 4-nitroaniline (IV) is in the range of 1: 0.5 to 1:1.
10. The process as claimed in claim 1, wherein said phase transfer catalyst is selected from the group consisting of tetra-n-butylammonium bromide, and crown ether.
11. The process as claimed in claim 1, wherein the mole ratio of said 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) to said phase transfer catalyst is in the range of 1: 0.01 to 1: 0.1.
12. The process as claimed in claim 1, wherein said second base is selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and triethyl amine.
13. The process as claimed in claim 1, wherein the mole ratio of said 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) to said second base is in the range of 1: 1 to 1: 3.
14. The process as claimed in claim 1, wherein said reducing agent is Raney nickel.
15. The process as claimed in claim 1, wherein the weight ratio of said 4-(4-nitrophenyl)morpholin-3-one (VI) to said reducing agent is in the range of 1: 0.01 to 1: 0.1.
16. A process for preparing 4-(4-aminophenyl)morpholin-3-one (I), said process comprising:
i. chlorinating 2-(2-chloroethoxy)acetic acid (II) using thionyl chloride in chlorobenzene at 50°C to obtain 2-(2-chloroethoxy)acetyl chloride (III);
ii. condensing said 2-(2-chloroethoxy)acetyl chloride (III) with 4-nitroaniline (IV) in methylene dichloride and in the presence of sodium carbonate at 25°C to obtain 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V);
iii. cyclizing said 2-(2-chloroethoxy)-N-(4-nitrophenyl)acetamide (V) in the presence of tetra-n-butyl ammonium bromide and sodium hydroxide at 20°C to obtain 4-(4-nitrophenyl)morpholin-3-one (VI); and
iv. reducing said 4-(4-nitrophenyl)morpholin-3-one (VI) using Raney nickel in dimethylformamide at 50°C, followed by purification to obtain 4-(4-aminophenyl)morpholin-3-one (I) having purity greater than 99%.