The present invention provides a process for the preparation of a compound of
Formula I.
F3C—CF?
>°
F3C (— F
CF3
Formula I
Background of the invention
The perfluoro-2-methyl-3-pentanone of Formula I is an important compound and
can be used as cleaning agent, solvent and extinguishant.
The Chinese Patent Application No. 102992986 describes a process for the preparation of perfluoro ethyl isopropylketone and its intermediates, perfluoro-2-methyl-2-pentene and perfluoro-2,3-epoxy-2-methyl pentane. The perfluoro-2-methyl-2-pentene is prepared by treating perfluoro-4-methyl-2-pentene with alkali metal fluoride, a phase transfer catalyst and a solvent. Further, perfluoro-2-methyl-2-pentene is treated with an oxidant, a phase transfer catalyst, a solvent and an additional catalyst to obtain perfluoro-2,3-epoxy-2-methylpentane. In the last step, perfluoro ethyl isopropylketone is prepared by treating the perfluoro-2,3-epoxy-2-methylpentane with a phase transfer catalyst and an additional catalyst. The additional catalyst mentioned are LiBr, Lil, KF, CsF, KHF2, PF5, SF4, titanium silicalite, phosphotungstic acid, KF/AI2O3, CsF/Al203, transition metal porphyrin complexes, Schiffer base, Mg-La composite oxide, one-component metal oxide, supported alkali metal or hydroxide, trimethylamine, dimethylaniline, pyridine N-oxide, trimethyl amine N-oxides, dimethyl formamide, dimethyl acetamide, diethyl benzamide, AlFnCl3-n and strongly acidic catalyst.

The described process suffers from the drawback that the use of additional catalyst results in effluent formation and hence arises difficultly to manage at industrial scale. Also, use of additional catalyst adds on to the cost thereby making the process industrially unfavourable.
While working on the present invention, the inventors have observed that, carrying out the reaction using phase transfer catalyst without additional catalyst overcomes the disadvantages associated with the prior arts. Thus, present invention provides a simple, economical and industrially feasible process.
Summary of the invention
The present invention provides a process for the preparation of a compound of
Formula I, comprising:
a) contacting a compound of Formula II with an alkali metal fluoride in the presence of acetonitrile and sulfolane to obtain a compound of Formula III,
b) contacting the compound of Formula III with an oxidant in the presence of a first phase transfer catalyst to obtain a compound of Formula IV,
c) contacting the compound of Formula IV with a second phase transfer catalyst to obtain the compound of Formula I, and
d) isolating the compound of Formula I obtained from step c),
wherein the step c) is carried out in the absence of an additional catalyst.
F F
H
F3C F
F3C CF2CF,,
H
F3C F

Formula II Formula III
F3C O CF2CF3
F3C

Formula IV Formula I
Detailed description of the invention
The present invention provides a process for the preparation of a compound of
Formula I, comprising:
a) contacting a compound of Formula II with an alkali metal fluoride in the presence of acetonitrile and sulfolane to obtain a compound of Formula III,
b) contacting the compound of Formula III with an oxidant in the presence of a first phase transfer catalyst to obtain a compound of Formula IV,
c) contacting the compound of Formula IV with a second phase transfer catalyst to obtain the compound of Formula I, and
d) isolating the compound of Formula I obtained from step c),
wherein the step c) is carried out in the absence of an additional catalyst.
F3C
F3C CF2CF,
F3C

Formula II Formula III
F3C O CF2CF3
F3C F
F3C—CF2
±°
F3C (— F
CF3
Formula IV Formula I
The compound of Formula II may be obtained commercially or may be prepared by any method known in the art.
The alkali metal fluoride in step a) is selected from the group consisting of sodium fluoride, potassium fluoride and cesium fluoride or a mixture thereof.
The step b) is carried out in presence of an oxidant selected from the group consisting of sodium hypochlorite, calcium hypochlorite, hydrogen peroxide, N-Oxide, preferably pyridine N-oxides, substituted pyridine N-oxides, n-alkyl morpholine N-oxides, trialkylamine N-oxides, quinoline N-oxides, substituted quinolone N-oxides, isoquinoline N-oxides, substituted isoquinoline N-oxides, pyrazine N-oxides, substituted pyrazine N-oxides, pyrimidine N-oxides, substituted pyrimidine N-oxides, pyridazine N-oxides, substituted pyridazine N-oxides, quinoxaline N-oxides, substituted quinoxaline N-oxides and Peracetic acid or a mixture thereof.
The first phase transfer catalyst used in step b) is selected from the group consisting of trioctyl methyl ammonium chloride, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, methyltricaprylammonium chloride,

methyltributylammonium chloride, crown ethers and urea or a mixture thereof. The step b) may take place in the presence of solvent, for example, acetonitrile.
The step c) is carried out in the presence of second phase transfer catalyst selected from the group consisting of tetrabutyl ammonium bromide and tetr am ethylethylenedi amine.
The step a) takes place at a temperature selected from 50°C to 155°C and in a time period selected from 0.5 hours to 10 hours. The step b) takes place at a temperature selected from -5°C to 25°C and in a time period selected from 0.5 hours to 12 hours. The step c) takes place at a temperature selected from 25°C to 30°C and in a time period selected from 15 minutes to 20 hours. An "additional catalyst" is a catalyst other than phase transfer catalyst. Additional catalyst may be acidic or basic catalyst.
The step a) to c) may be carried out as "one-pot process" to obtain the compound of Formula I from the compound of Formula II directly without isolation of compound of formula III and compound of formula IV.
The compound of Formula I is isolated by any of the methods known in the art, for example, distillation, evaporation and layer separation or mixture thereof.
While the present invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Examples

Example 1: Preparation of 1.1.1.3.4.4.5.5.5-nonafluoro-2-(trifluoromethyl)pent-2-ene
Acetonitrile (90 g, 2.19 mol) and dry potassium fluoride (50 g, 0.86 mol) were taken in reactor, hermetically sealed and stirred at 300 rpm. The hexafluoro propene (300 g, 2.00 mol) was added portion-wise through vent at 55°C. After addition of hexafluoro propene, sulfolane (170 g, 1.41 mol) was added into the reactor at 55°C and the temperature of the reactor was raised to 155 °C. After 10 hours of stirring, organic layer was separated to obtain the title compound.
Yield 84%
Purity: 91.0% (by Gas chromatography)
Example 2: Preparation of 2-fluoro-2-(pentafluoroethyl)-3.3-
bis(trifluoromethyl)oxirane
Acetonitrile (23 g, 0.56 mol), aqueous sodium hypochlorite (350g, 10%) and trioctyl methyl ammonium chloride (0.76 g, 0.01 mol) were taken in 500 mL round bottom flask fitted with condenser and stirrer. The 1,1,1,3,4,4,5,5,5-nonafluoro-2-(trifluoromethyl)pent-2-ene (50 g, 0.17 mol) was added in lots to the reaction mixture at 0°C and the temperature of the mixture was maintained in the range of 0°C to 5°C. After 3.5 hours of stirring, organic layer was separated to obtain the title compound.
Yield (%) = 74
Purity (%): 95 (by Gas chromatography)
Example 3: Preparation of 1.1.1.2.2.4.5.5.5-nonafluoro-4-(trifluoromethyl)pentan-3-one
The 2-fluoro-2-(pentafluoroethyl)-3,3-bis(trifluoromethyl)oxirane (50 g, 0.16 mol), tetrabutyl ammonium bromide (5.1 g, 0.016 mol) and diglyme (47 g, 0.35 mol) were added in 250mL round bottom flask fitted with reflux condenser and

magnetic stirrer. The reaction mass was stirred at a temperature of 25°C to 30°C. After 15 hours, organic layer was separated to obtain the title compound.
Yield (%): 64
Purity (%): 99 (by Gas chromatography)

We claim:
A. process for the preparation of a compound of Formula I, comprising:
a) contacting a compound of Formula II with an alkali metal fluoride in the presence of acetonitrile and sulfolane to obtain a compound of Formula III,
b) contacting the compound of Formula III with an oxidant in the presence of a first phase transfer catalyst to obtain a compound of Formula IV,
c) contacting the compound of Formula IV with a second phase transfer catalyst to obtain the compound of Formula I, and
d) isolating the compound of Formula I obtained from step c),
wherein the step c) is carried out in the absence of an additional catalyst.
F3C
F3C CF2CF,
F3C
Formula II Formula III
F3C O CF2CF3
F3C

Formula IV

Formula I

2. The process as claimed in claim 1, wherein the alkali metal fluoride used in step a) is selected from the group consisting of sodium fluoride, potassium fluoride and cesium fluoride or a mixture thereof.
3. The process as claimed in claim 1, wherein the oxidant used in step b) is selected from the group consisting of sodium hypochlorite, calcium hypochlorite, hydrogen peroxide, N- Oxide, preferably pyridine N-oxides, substituted pyridine N-oxides, n-alkyl morpholine N-oxides, trialkylamine N-oxides, quinoline N-oxides, substituted quinolone N-oxides, isoquinoline N-oxides, substituted isoquinoline N-oxides, pyrazine N-oxides, substituted pyrazine N-oxides, pyrimidine N-oxides, substituted pyrimidine N-oxides, pyridazine N-oxides, substituted pyridazine N-oxides, quinoxaline N-oxides, substituted quinoxaline N-oxides and peracetic acid or a mixture thereof.
4. The process as claimed in claim 1, wherein the first phase transfer catalyst used in step b) is selected from the group consisting of trioctyl methyl ammonium chloride, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, methyltricaprylammonium chloride, methyltributylammonium chloride, crown ethers and urea or a mixture thereof.
5. The process as claimed in claim 1, wherein the second phase transfer catalyst used in step c) is selected from the group consisting of tetrabutyl ammonium bromide and tetramethylethylenediamine.
6. The process as claimed in claim 1, wherein the additional catalyst is a catalyst other than phase transfer catalyst.
7. The process as claimed in claim 1, wherein the step a) takes place at a
temperature selected from 50°C to 155°C and in a time period selected from 0.5
hours to 10 hours.

8. The process as claimed in claim 1, wherein the step b) takes place at a temperature selected from -5°C to 25°C and in a time period selected from 0.5 hours to 12 hours.
9. The process as claimed in claim 1, wherein the step c) takes place at a temperature selected from 25°C to 30°C and in a time period selected from 15 minutes to 12 hours.
10. The process as claimed in claim 1, wherein the process for preparation of
compound of Formula I from compound of formula II is optionally a one pot
process.