Description:FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“PROCESS FOR PREPARATION OF METHYLENE-1,3-DIOXOLANES”

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

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention provides a process for preparing methylene-1,3-dioxolanes, that are important intermediates for preparing pyrazoles and anthranilic acid amides, which are an important class of insecticides.

BACKGROUND OF THE INVENTION
Methylene-1,3-dioxolanes are important intermediates for preparing pyrazoles and anthranilic acid amides are used as insecticides.
Journal of Polymer Science 1964, vol. 2 p.3471 and Biochemical preparation, 1960 v. 7, 45, discloses a process for preparation of 2,2-dimethyl-4-methylene-1,3-dioxolane by reacting 4-chloromethylene-1,3-dioxolanes with solid potassium hydroxide in low yield.
U.S. Pat. No. 9,029,577 discloses a process for preparation of methylene-1,3-dioxolanes by reacting 4-chloromethylene-1,3-dioxolanes with an inorganic base in presence of one or more polyethylene glycol dimethyl ethers or polyethylene glycol diethyl ethers.
The methods known in the literature either provide low yields or use costly solvents such as polyethylene glycol dimethyl ethers, and reagents, which are not easily available.
The present invention provides a highly selective and industrially viable process for the preparation of methylene-1,3-dioxolanes with high purity and yield.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a simple, cost effective and environment friendly process for the preparation of methylene-1,3-dioxolanes using easily available solvents and reagents.

SUMMARY OF THE INVENTION
The present invention provides a process for preparation of methylene-1,3-dioxolanes using easily available solvents and reagents.

DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for preparation of methylene-1,3-dioxolanes of formula I,

where R1 and R2 independently of one another are hydrogen, alkyl, aryl or alkylaryl, may also form, together with the carbon atom to which they are linked, a 4- to 7-membered, saturated, optionally substituted ring,
comprising a step of reacting a compound of formula II,

where R1 and R2 are as defined above,
with one or more inorganic bases in presence of one or more polyethylene glycols.
In an embodiment of the present invention, the inorganic base is selected from a group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium isopropoxide, potassium isopropoxide, sodium tert-butoxide, and potassium tert-butoxide or a mixture thereof.
In another embodiment of the present invention, polyethylene glycol used have a molecular mass ranging from 200 to 1000 atomic mass unit.
In another embodiment of the present invention, polyethylene glycol used is selected from a group consisting of PEG-200, PEG-300, PEG-400, PEG-500, PEG-600, and PEG-1000 or the like
In another embodiment of the present invention, the reaction of the compound of formula II with an inorganic base is carried out at a temperature of 90°C to 120°C.
In another embodiment of the present invention, the inorganic base is used in a mole ratio of 0.9 to 2.0 with respect to the compound of formula II.
In another embodiment of the present invention, polyethylene glycol is used in an amount of one to four times with respect to the compound of formula II.
In an embodiment, the present invention provides a process for preparation of methylene-1,3-dioxolanes of formula I, having yield greater than 80 to 95%.
In an embodiment, the present invention provides a process for preparation of methylene-1,3-dioxolanes of formula I, having purity greater than 97%, preferably greater than 98%, more preferably greater than 99%, having impurities in an amount of 0.1 to 0.5%, wherein impurities refer to isomers of product.
In another embodiment of the present invention, the solvent used or generated in the reaction is recovered and recycled for subsequent reactions.
The compound of formula II used in the present invention may be prepared by any method known in the literature or may be obtained commercially.
The product may be isolated by any method known in the art, for example, chemical separation, extraction, acid-base neutralization, distillation, recrystallization, 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.
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.
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 2,2-dimethyl-4-methylidene-1,3-dioxolane
4-(Chloromethyl)-2,2-dimethyl-1,3-dioxolane (200g) and PEG 600 (500g) were charged in a 1000ml reactor. Sodium hydroxide (110g) was dumped in the reactor under nitrogen atmosphere with stirring. The reaction was gradually heated to 110? and reaction monitoring sample was checked on gas chromatography. After reaction, the heating was stopped and reaction mass was distilled to obtain 2,2-dimethyl-4-methylidene-1,3-dioxolane (138.5g). The bottom mass containing PEG 600 along with inorganics salts were filtered at elevated temperature of 60-90? before recycling in subsequent batches.
Yield: 91.4%
Purity: 99.1%

Example 2: Preparation of 2,2-dimethyl-4-methylidene-1,3-dioxolane
4-(Chloromethyl)-2,2-dimethyl-1,3-dioxolane (200g) and PEG 200 (500g) were charged in a 1000ml reactor. Sodium hydroxide (110g) was added in the reactor under nitrogen atmosphere with stirring. The reaction was gradually heated to 110? and reaction monitoring sample was checked on gas chromatography. After reaction, the heating was stopped and reaction mass was distilled to obtain 2,2-dimethyl-4-methylidene-1,3-dioxolane (136.8g). The bottom mass containing PEG 200 along with inorganics salts were filtered at elevated temperature of 60-90? before recycling in subsequent batches.
Yield: 90%
Purity: 99.1%
Example 3: Preparation of 2,2-dimethyl-4-methylidene-1,3-dioxolane
4-(Chloromethyl)-2,2-dimethyl-1,3-dioxolane (200g) and PEG 1000 (500g) were charged in a 1000ml reactor. Sodium hydroxide (110g) was added in the reactor under nitrogen atmosphere with stirring. The reaction was gradually heated to 110? and reaction monitoring sample was checked on gas chromatography. After reaction, the heating was stopped and reaction mass was distilled to obtain 2,2-dimethyl-4-methylidene-1,3-dioxolane (136g). The bottom mass containing PEG 1000 along with inorganics salts were filtered at elevated temperature of 60-90? before recycling in subsequent batches.
Yield: 89.5%
Purity: 99.1%
, Claims:
WE CLAIM:
1. A process for preparation of methylene-1,3-dioxolanes of formula I,

where R1 and R2 independently of one another are hydrogen, alkyl, aryl or alkylaryl, may also form, together with the carbon atom to which they are linked, a 4- to 7-membered, saturated, optionally substituted ring,
comprising a step of reacting a compound of formula II,

where R1 and R2 are as defined above,
with one or more inorganic bases in presence of one or more polyethylene glycols.
2. The process as claimed in claim 1, wherein the inorganic base is selected from a group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium isopropoxide, potassium isopropoxide, sodium tert-butoxide, and potassium tert-butoxide or a mixture thereof.
3. The process as claimed in claim 1, wherein the polyethylene glycol used have a molecular mass ranging from 200 to 1000 atomic mass unit.
4. The process as claimed in claim 1, wherein the process is carried out at a temperature of 90°C to 120°C.
5. The process as claimed in claim 1, wherein the inorganic base is used in a mole ratio of 0.9 to 2.0 with respect to the compound of formula II.
6. The process as claimed in claim 1, wherein the polyethylene glycol is used in an amount of one to four times with respect to the compound of formula II.

Dated this 15th day of December 2022