Claims:WE CLAIM:
1. A process for preparation of an alkenone ether of Formula I, comprising;
R1COCH=CH-OR2
Formula 1
wherein R1 represents a methyl substituted by at least one fluorine; R2 represents methyl or ethyl group.
a) reacting a compound of Formula II and a compound of Formula III in presence of a base, and
R1COX CH2=CH-OR2
Formula II Formula III
wherein X represents fluorine, chlorine, iodine or bromine; R1 and R2 are as defined above.
b) isolating the alkenone ether of Formula I.
2. The process as claimed in claim 1, comprising,
a) reacting a compound of Formula II and a compound of Formula III in presence of a base to form a solution,
R1COX CH2=CH-OR2
Formula II Formula III
wherein X represents fluorine, chlorine, iodine or bromine; R1 and R2 are as defined above.
b) distilling the reaction solution of step a) to obtain a residue;
c) introducing alkali hydroxide into the residue of step b); and
d) isolating alkenone ether of Formula I with recovery of the base, wherein the recovery of base is more than 90%.
10
3. The process as claimed in claim 2, wherein the recovery of base is more than 95%.
4. The process as claimed in claim 1 & 2, wherein the isolation of alkenone ether of Formula I and recovery of base is carried out without using water.
5. The process as claimed in claim 2, wherein the ‘alkali hydroxide’ is selected from a group consisting of sodium hydroxide, potassium hydroxide, cesium hydroxide and magnesium hydroxide.
6. The process as claimed in claim 1 & 2, wherein the reaction of the compound of Formula II and the compound of Formula III is carried out without using any solvent.
7. The process as claimed in claim 1 & 2, wherein the ‘base’ is selected from a group consisting of diisopropylethyl amine (DIPEA), pyridine, N-methylpyrrolidine, N,N-dimethylaniline, 2,2,6,6-tetramethylpipridine, N,N'-dimethylpropylene urea (DMPU), 1,8-diazabicyclo[5.4. 0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO) and tributylamine or a mixture thereof.
8. The process as claimed in claim 1 & 2, wherein the molar ratio of the base w.r.t the compound of formula III is in the range of 0.28-0.35.
9. The process as claimed in claim 1 & 2, wherein the reaction of the compound of Formula II and the compound of Formula III is carried out at a temperature of 30°C to 35°C.

, Description:FORM 2

THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

AN IMPROVED PROCESS FOR PREPARATION OF ALKENONE ETHERS
The present application is an improvement over the invention claimed in the complete specifications of the main patent no. IN330999 granted on 31-01-2020

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (INDIA)

The following specification describes the invention.
1
FIELD OF THE INVENTION
The present invention relates to an improved process for preparation of alkenone ethers.

BACKGROUND OF THE INVENTION
The alkenone ethers, such as 4-alkoxy-1,1,1-trifluoro-3-buten-2-one, are building blocks and important precursors for preparation of agrochemicals or pharmaceuticals.
The U.S. Patent No. 8,552,221 provides a process for preparation of halogenated alkenone ethers by reacting a trifluoroacetyl chloride with vinyl ether in a liquid reaction medium under turbulent conditions.
The U.S. Patent No. 7,057,079 provides a process for production of alkenone from vinyl ethers and acid halides or acid anhydrides in the presence of "onium" salt of carboxylic acid. All the processes involve water work up that results in yield loss and also increases the effluent load.
The present invention provides an effluent free process for preparation of alkenone ethers.

OBJECT OF THE INVENTION
The main object of present invention is to provide a cost-effective and a scalable process for preparation of alkenone ethers by using a suitable base that facilitates recovery of the product without water workup. This process reduces the effluent load, ensures maximum recovery of the base therefore increases the overall efficiency of the process at industrial scale.

2
SUMMARY OF THE INVENTION
The present invention provides an improved process for preparation of an alkenone ether of Formula I, comprising;
R1COCH=CH-OR2
Formula 1
wherein R1 represents a methyl substituted by at least one fluorine; R2 represents methyl or ethyl group
a) reacting a compound of Formula II and a compound of Formula III in presence of a suitable base, and
R1COX CH2=CH-OR2
Formula II Formula III
wherein X represents fluorine, chlorine, iodine or bromine; R1 and R2 are as defined above
b) isolating alkenone ether of Formula I.

DETAILED DESCRIPTION OF THE INVENTION
As used herein, ‘alkali hydroxide’ may be selected from a group consisting of sodium hydroxide, potassium hydroxide, cesium hydroxide and magnesium hydroxide or like.
In an embodiment, the reaction of a compound of Formula II and a compound of Formula III is carried out in absence of a solvent. The absence of an organic solvent in the process eliminates the formation of by-products.
In another embodiment, the reaction of a compound of Formula II and a compound of Formula III is carried out in the presence of a suitable base.
3
In an embodiment, the molar ratio of a suitable base w.r.t the compound of formula III is in the range of 0.28-0.35. In another embodiment, the reaction of a compound of Formula II and a compound of Formula III is carried out at a temperature of 30°C to 35°C.
The ‘suitable base’ is selected from a group consisting of diisopropylethyl amine (DIPEA), pyridine, N-methylpyrrolidine, N,N-dimethylaniline, 2,2,6,6-tetramethylpipridine, N,N'-dimethylpropylene urea (DMPU), 1,8-diazabicyclo[5.4. 0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), tributylamine and a mixture thereof.
In another embodiment, the reaction of compound of Formula II and a compound of Formula III is carried out in the presence of DIPEA as a base.
In an embodiment of the present invention, the product in the present invention is isolated without water work-up. The water work-up refers to extraction of salts in water and extraction of product in the organic solvent followed by partitioning of layers and subsequent isolation of the product from the organic solvent by distillation. The process of the present invention eliminates aqueous effluent and thus provides an environment friendly option for preparation of alkenone ethers. The process of present invention also eliminates the use of organic solvent therefore provides a cost effective alternative at commercial scale.

4
In another embodiment, the present invention provides an improved process for preparation of alkenone ether of Formula I with recovery of the base, comprising;
R1COCH=CH-OR2
Formula 1
wherein R1 represents a methyl substituted by at least one fluorine; R2 represents methyl or ethyl group
a) reacting a compound of Formula II and compound of Formula III in presence of a suitable base to form a solution,
R1COX CH2=CH-OR2
Formula II Formula III
wherein X represents fluorine, chlorine, iodine or bromine; R1 and R2 are as defined above
b) distilling the reaction solution of step a) to obtain a residue;
c) introducing alkali hydroxide into the residue of step b);
d) isolating alkenone ether of Formula I with recovery of the base, wherein recovering of the base is more than 95%.
The process of present invention provides an excellent recovery of the base thus considerably reduces the cost of running the process at commercial scale without compromising on the yield and purity of the product.
The compound of formula I is isolated in a purity of 90% to 98% with a yield of 80 to 85%. The recovery of base is greater than 90% and preferably 95%. The process eliminates generation of waste and reduces the cost of its disposal and therefore provides an economically more viable alternative.
PCT Publication no. WO2015011728, discloses a process for preparation of alkenone ethers using triethyl amine (TEA) as a base. The inventors of the present
5
have performed an experiment using other suitable bases and achieved recovery more than 95% of that base.
The reaction of a compound of Formula II and a compound of Formula III may optionally take place in the presence of an organic solvent.
The organic solvent may be selected from aromatic hydrocarbon such as benzene, toluene or xylene and a mixture thereof; an aliphatic hydrocarbon such as pentane or hexane and mixture thereof; a halogenated hydrocarbon such as methylene chloride, chloroform, ethylene chloride or carbon tetrachloride and mixture thereof; an ether such as diethyl ether, dibutyl ether, tetrahydrohran or dioxane and mixture thereof.
The compound of the present invention can be isolated using various isolation techniques known in the art, for example, chemical separation, extraction, acid-base neutralization, distillation, evaporation, column chromatography and filtration or a mixture thereof.
The completion of the reaction may be monitored by any one of chromatographic techniques such as thin layer chromatography (TLC), high pressure liquid chromatography (HPLC), ultra-pressure liquid chromatography (UPLC), gas chromatography (GC), liquid chromatography (LC) and alike. The compound of formula II, III and reagents used in the above process are obtained commercially.
Unless stated to the contrary, any of the words “comprising”, “comprises” and includes mean “including without limitation” and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it.
Embodiments of the invention are not mutually exclusive but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
6
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLES
Example 1: Preparation of 4-ethoxy-1,1,l-trifluoro-3-buten-2-one
A mixture of ethyl vinyl ether (250 g, 3.467 mol) and tributylamine (212.07 g, 1.143 mol) was charged in an autoclave. The mixture was cooled to 10°C and then trifluoroacetyl fluoride gas (440 g, 3.79 mol) was purged into the reaction mixture and the temperature was maintained at 30°C to 35°C. Thereafter, the reaction mixture was stirred at 30°C for 2-3 hours to get crude product, further followed by distillation at 40-50°C under vacuum (1-2 mmHg) to obtain the pure product (545g).
Yield (%): 91.91
Purity (%): 98.29
Example 2: Preparation of 4-ethoxy-1,1,l-trifluoro-3-buten-2-one
A mixture of ethyl vinyl ether (250 g, 3.467 mol) and diisopropylethyl amine (156.82 g, 1.212 mol) was charged in an autoclave. The mixture was cooled to 10°C and then trifluoroacetyl fluoride gas (440 g, 3.788 mol) was purged into a reaction mixture and the temperature was maintained at 30°C to 35°C. Thereafter, reaction mixture was stirred at 30°C for 2-3 hours to get crude product, further followed by distillation at 40-50°C under vacuum (1-2 mmHg) to obtain the pure product (549g).
Yield (%): 92.49
Purity (%): 98.2

7
Example 3: Preparation of 4-ethoxy-1,1,l-trifluoro-3-buten-2-one
A mixture of ethyl vinyl ether (250 g, 3.467 mol) and N,N'-dimethylpropylene urea (177.78 g, 1.386 mol) was charged in an autoclave. The mixture was cooled to 10°C and then trifluoroacetyl fluoride gas (438 g, 3.77 mol) was purged into a reaction mixture and the temperature was maintained at 30°C to 35°C. Thereafter, reaction mixture was stirred at 30°C for 2-3 hours to get crude product, further followed by distillation at 40-50°C under vacuum (1-2 mmHg) to obtain the pure product (538g).
Yield (%): 90.44; Purity (%): 97.98
Example 4: Recovery of diisopropylethylamine:
After distillation, bottom of distillation from example 2 containing N,N-diisopropylethylamine trihydrofluoride (223g) was charged into 1000 ml of 3-neck reactor and cooled to 15-20°C using an ice bath. Thereafter a solution of 40% aqueous potassium hydroxide (442.7g) was added dropwise over one hour in the flask to get a layered solution, top N,N-diisopropylethylamine layer was separated out from the solution and subjected to distillation to afford pure N,N-diisopropylethylamine (DIPEA).
Purity of recovered DIPEA: 99.75%; DIPEA recovery: 94.86%
Dated this 5th day of March 2021.

8

ABSTRACT
AN IMPROVED PROCESS FOR PREPARATION OF ALKENONE ETHERS
The present invention relates to an improved process for the preparation of alkenone ethers of Formula I,
R1COCH=CH-OR2
Formula 1
wherein, R1 represents a methyl substituted by at least one fluorine; R2 represents methyl or ethyl group.
The alkenone ethers, such as 4-alkoxy-1,1,1-trifluoro-3-butenone, are building blocks and important precursors for preparation of agrochemicals or pharmaceuticals.

9
WE CLAIM:
1. A process for preparation of an alkenone ether of Formula I, comprising;
R1COCH=CH-OR2
Formula 1
wherein R1 represents a methyl substituted by at least one fluorine; R2 represents methyl or ethyl group.
a) reacting a compound of Formula II and a compound of Formula III in presence of a base, and
R1COX CH2=CH-OR2
Formula II Formula III
wherein X represents fluorine, chlorine, iodine or bromine; R1 and R2 are as defined above.
b) isolating the alkenone ether of Formula I.
2. The process as claimed in claim 1, comprising,
a) reacting a compound of Formula II and a compound of Formula III in presence of a base to form a solution,
R1COX CH2=CH-OR2
Formula II Formula III
wherein X represents fluorine, chlorine, iodine or bromine; R1 and R2 are as defined above.
b) distilling the reaction solution of step a) to obtain a residue;
c) introducing alkali hydroxide into the residue of step b); and
d) isolating alkenone ether of Formula I with recovery of the base, wherein the recovery of base is more than 90%.
10
3. The process as claimed in claim 2, wherein the recovery of base is more than 95%.
4. The process as claimed in claim 1 & 2, wherein the isolation of alkenone ether of Formula I and recovery of base is carried out without using water.
5. The process as claimed in claim 2, wherein the ‘alkali hydroxide’ is selected from a group consisting of sodium hydroxide, potassium hydroxide, cesium hydroxide and magnesium hydroxide.
6. The process as claimed in claim 1 & 2, wherein the reaction of the compound of Formula II and the compound of Formula III is carried out without using any solvent.
7. The process as claimed in claim 1 & 2, wherein the ‘base’ is selected from a group consisting of diisopropylethyl amine (DIPEA), pyridine, N-methylpyrrolidine, N,N-dimethylaniline, 2,2,6,6-tetramethylpipridine, N,N'-dimethylpropylene urea (DMPU), 1,8-diazabicyclo[5.4. 0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO) and tributylamine or a mixture thereof.
8. The process as claimed in claim 1 & 2, wherein the molar ratio of the base w.r.t the compound of formula III is in the range of 0.28-0.35.
9. The process as claimed in claim 1 & 2, wherein the reaction of the compound of Formula II and the compound of Formula III is carried out at a temperature of 30°C to 35°C.

11