Field of the invention
5
The present invention provides a process for the preparation of pure methyl 2-fluoroacrylate.
Background of the invention
10 The methyl 2-fluoroacrylate is a key intermediate for agrochemicals and pharmaceuticals.
The crossed Claisen condensation of alkyl monofluoroacetates with esters of formic acid or
oxalic acid in the presence of strong bases, followed by a reaction with paraformaldehyde
represents one of the most widely used methods for the synthesis of α-fluoroacrylates.
F
H2C
O
CH3
15 O
Methyl 2-fluoroacrylate
The PCT publication no. 2014/001365 provides a process for the manufacture of an
alkylfluoroacrylate, by reacting an alkylfluoroacetate with an ester of formic acid or oxalic
20 acid in the presence of a base in a crossed Claisen condensation resulting in a Claisen salt.
The Claisen salt is reacted with paraformaldehyde to isolate alkylfluoroacrylate, using an
alkane as solvent. The process disclosed suffers from the disadvantages that the isolated
methyl fluoroacrylate contains residual methyl fluoroacetate and solvents. Hence,
purification of methyl fluoroacrylate (boiling point 91°C) by distillation from residuals such
25 as methyl fluoroacetate (boiling point 104°C) and methyl acrylate (boiling point 80°C) poses
a challenge because of very close boiling points. Additionally, distillation has to be done
under high vacuum and at a temperature less than 45°C, as the methyl-2-fluoroacrylate has a
tendency to polymerize quickly at a temperature beyond 45°C.
2
The inventors have surprisingly found that purity of methyl 2-fluoroacrylate containing unsaturated compounds as impurity, can be improved by reaction with halogen or interhalogen. The unsaturated compounds may be methyl acrylate, methyl difluoroacrylate, methyl chlorofluoroacrylate and methyl chloroacrylate among others. The unsaturated 5 compound present in methyl fluoroacrylate is converted to corresponding methyl halopropanoate on reaction with halogen or interhalogens. Such methyl halopropanoates have a boiling point between 170°C to 240°C, which is much higher than the boiling of methyl fluoroacrylate, that is, 91°C. Hence, the separation of the methyl 2-fluoroacrylate becomes easier thereby simplifying the distillation part. 10
It is therefore, the present invention provides a process for the preparation of pure methyl 2-fluoroacrylate having purity of 99% or more. The present invention provides a process of purification of methyl 2-fluoroacrylate which is simple, economically viable and industrially doable, in comparison to prior arts. 15
Summary of the invention
The present invention provides a process for the preparation of pure methyl 2-fluoroacrylate having purity of 99% or more, comprising; 20
a) contacting methyl 2-fluoroacrylate having purity of 95% or less, with a halogen or an interhalogen; and
b) isolating methyl 2-fluoroacrylate having purity of 99% or more, from step a).
25
Detailed description of the invention
The present invention provides a process for the preparation of pure methyl 2-fluoroacrylate having purity of 99% or more, comprising;
a) contacting methyl 2-fluoroacrylate having purity of 95% or less, with a halogen or 30 an interhalogen; and
b) isolating methyl 2-fluoroacrylate having purity of 99% or more, from step a).
3
The contacting of methyl 2-fluoroacrylate having purity of 95% or less, with halogen or interhalogen may be carried out at a temperature in the range of 0oC to 30oC. The halogen is selected from the group consisting of fluorine, chlorine, bromine and iodine or mixture thereof. 5
The term “interhalogen” used in the specification refers to those compounds which are formed by the union of two different halogens. The general formula of most interhalogen compounds is XYn, where n = 1, 3, 5 or 7, and X is the less electronegative of the two halogens. The interhalogen is selected from the group consisting of chlorine monofluoride, 10 bromine monochloride, iodine monochloride, iodine monobromide, chlorine trifluoride, bromine trifluoride, iodine trichloride, chlorine pentafluoride, bromine pentafluoride and iodine pentafluoride or mixtures thereof.
The methyl 2-fluoroacrylate having purity of 95% or less may be obtained commercially or 15 may be prepared by any of the methods known in the art, for example, as in the PCT publication no.2014/001365. The methyl 2-fluoroacrylate having purity of 95% has unsaturated compounds as impurity. The unsaturated compounds may be methyl acrylate, methyl difluoroacrylate, methyl chlorofluoroacrylate and methyl chloroacrylate among others. 20
The methyl 2-fluoroacrylate purified using the process of the present invention has a purity greater than 99% by gas chromatography, preferably greater than 99.5%.
The isolation of the pure methyl fluoroacrylate is carried out by distillation, evaporation, and 25 layer separation or mixture thereof. The purity of methyl 2-fluoroacrylate is determined by Agilent 6890 Gas Chromatograph with flame ionization detector.
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 30 be included within the scope of the present invention. 4
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Examples
5
Example 1: Purification of methyl 2-fluoroacrylate
220 g of reaction mass containing methyl acrylate and methyl 2-fluoroacrylate (95% purity) was taken in a reaction vessel. Bromine (26g) was added slowly to the reaction mass over the period of 2 hours at a temperature in the range of 5°C to 10°C. The temperature of the reaction mass was raised to 30°C and the reaction was monitored by gas chromatography. 10 The reaction mass was distilled to obtain the title compound.
Yield (%): 85
Purity (%) = 99
15
20
25 5
We claim:
1. A process for the preparation of pure methyl 2-fluoroacrylate having purity of 99% or more, comprising;
a) contacting methyl 2-fluoroacrylate having purity of 95% or less, with a halogen or an interhalogen; and 5
b) isolating methyl 2-fluoroacrylate having purity of 99% or more, from step a).
2. The process as claimed in claim 1, wherein step a) is carried out at a temperature in the range of 0oC to 30oC.
3. The process as claimed in claim 1, wherein the halogen is selected from the group 10 consisting of fluorine, chlorine, bromine and iodine or mixture thereof.
4. The process as claimed in claim 1, wherein the interhalogen is selected from the group consisting of chlorine monofluoride, bromine monochloride, iodine monochloride, iodine monobromide, chlorine trifluoride, bromine trifluoride, iodine trichloride, chlorine pentafluoride, bromine pentafluoride and iodine pentafluoride or 15 mixture thereof.
5. The process as claimed in claim 1, wherein the isolation of the pure methyl fluoroacrylate is carried out by a distillation, evaporation, and layer separation or mixture thereof.