ITMI20011344A1 - PROCEDURE FOR THE PREPARATION OF 1,3-DIOSSOLAN-2-ONI - Google Patents

Description

Description of the invention which is entitled:

"Process for the preparation of 1,3-dioxolan-2-oni"

The present invention relates to a new process for the preparation of 1,3-dioxolan-2-oni variously substituted.

The 1, 3-dioxolan-2-oni, belonging to the chemical class commonly called "cyclic carbonates", are important industrial intermediates useful for the preparation of almost completely non-toxic solvents and monomers for the synthesis of variously substituted polycarbonates, polyurethanes and polyesters, for example by reaction with anhydrides, such as phthalic anhydride among others. Polycarbonates which are widely used in the preparation of rigid objects, used for example as parts of machines, are obtained by polymerization of methacryl dioxolane.

The most widely used synthesis of the 1,3-dioxolan-2-ones is carried out by the reaction between an appropriate epoxide and carbon dioxide, in the presence of various catalysts and solvents such as dimethylformamide or aromatic hydrocarbons. Recently, syntheses have been described which employ catalysts based on alkali halides (J. Org. Chem., 1993, 58: 6198-6202), mixed oxides of aluminum and magnesium (J. Chem. Soc., Chem.

Commun., 1997, 1129-1130) and magnesium oxide (J. Am. Chem. Soc., 1999, 121: 4526-4527).

Again starting from epoxides and carbon dioxide, syntheses of 1,3-dioxolan-2-oni have been described under various reaction conditions:

WO 84/00371 describes the reaction in the presence of triphenyl phosphine as catalyst operating at a pressure of 21 bar and using alcohol as solvent;

US 3,748,345 describes the reaction in the presence of nickel complexes with phosphines as catalysts at a pressure of 35 bar to give 50% of the conversion of the epoxide into cyclic carbonate;

EP 0 212 409 describes the use of catalysts such as amines, ammonium salts, phosphines and co-catalysts to increase the reaction rate;

US 4,892,954 describes the reaction with catalysts such as phosphines, ammonium salts and amines at temperatures between 60 and 180 ° C;

US 5,153,333 describes the use of phosphonium salts as catalysts and temperatures between 60 and 200 ° C and at pressures between 1 and 5 atmospheres; finally RU 2128658 describes the use of cobalt halides as catalysts, temperatures between 130 and 150 ° C and dimethylformamide as solvent.

All the synthesis processes described above have various drawbacks such as high temperatures, the use of toxic or volatile solvents (called VOC from the English "volatil organic solvents") which must then be separated from the reaction products and catalysts, or again the contamination of the final cyclic carbonate with the metal catalyst used in the reaction. Consequently, the known processes require additional reaction steps for the purification of the final product, be it for example a further distillation or crystallization, or even investments in special equipment necessary for the reactions at high pressures and all these factors contribute to aggravate the production costs that become even critical when it comes to synthesis on an industrial scale.

The object of the present invention is to provide an innovative synthesis of cyclic carbonates, in particular for variously substituted 1,3-dioxolan-2-oni, which overcomes the drawbacks reported above and which provides such products with high yields.

A first object of the present invention is therefore a process for the preparation of a variously substituted 1, 3-dioxolan-2-one of formula (I)

wherein R is equal to hydrogen or represents from 1 to 4 substituents, the same or different from each other, which comprises

- reacting an epoxide of formula (II)

where R is defined as above, with carbon dioxide (CO2), at atmospheric pressure, in a solvent selected from tetrabutylammonium bromide (TBAB) and a mixture of tetrabutylammonium bromide (TBAB) and tetrabutylammonium iodide (TBAI), at a temperature greater than or equal to 110 ° C e

optionally isolate the 1,3-dioxolan-2-one of formula (I) thus obtained.

In the present description the term "atmospheric pressure" designates a pressure of about 760 mmHg, the modest variations due for example to environmental factors being included in the definition.

The reaction temperature must be equal to or higher than the melting temperature of the TBAB solvent or of the TBAB / TBAI mixture; in general, a temperature of 110 ° C is sufficient, the temperature of about 120 ° C being preferred as it allows the conversion speed to be increased. If desired, higher temperatures can be employed although they are not necessary for carrying out the reaction which is complete in a few hours.

The reaction can alternatively be carried out in TBAB alone or in a TBAB / TBAI mixture. The addition of TBAI allows to increase the reaction rate and the quantity of TBAI to be used can therefore be freely chosen taking into account the fact that TBAI slightly increases the melting point of the solvent mixture and is also more expensive than TBAB. According to a preferred aspect, the mixture of TBAB / TBAI solvents is about 1/1 by weight, a ratio which allows to operate at sufficiently low temperatures and at the same time to obtain good reaction rates.

According to a further preferred aspect of the invention, R represents one or two substituents, independently selected from aryls and alkyls, optionally substituted, for example with ester or ether radicals.

Illustrative examples of R substituents are as follows:

phenyl-;

benzyl-;

in which

R 'is chosen from

R "is selected from phenyl, benzyl and alkyl, Falchyl being able to be linear or branched.

According to an advantageous aspect of the invention, R represents a single substituent.

To carry out the reaction of the invention, no catalysts or co-solvents are required and the conversion of epoxide (II) into cyclic carbonate (I) is usually quantitative and does not produce significant quantities of by-products deriving from the polymerization of the epoxide (II ).

Furthermore, it is not necessary to add polymerization inhibitors such as hydroquinone, for example in the conversion of glycidyl methacrylate, since such polymerizations do not take place during the reaction of the invention.

The reaction is normally complete within a few hours, generally 0.5 to 6 hours are sufficient to obtain the complete conversion, in some cases the reaction is complete already after one hour.

The isolation of 1,3-dioxolan-2-one can be carried out according to the methods known to those skilled in the art. For example, simple distillation under reduced pressure provides separation from the solvent employed.

Alternatively, the obtained 1,3-dioxolan-2-one can be separated by extraction with solvents immiscible in the reaction solvents TBAB and / or TBAI, for example with ethyl acetate or cyclohexane.

The reaction solvents TBAB and TBAI have almost zero vapor pressure and can therefore be reused several times after the 1,3-dioxolan-2-one separation.

The following examples illustrate the invention in a non-limiting way. EXAMPLE 1

4-Phenoxymethyl-1,3-dioxolan-2-one

60 g of a 1/1 weight mixture of TBAB and TBAI and 20 g of glycidyl phenyl ether are poured into a 200 ml glass flask equipped with a thermometer, magnetic stirrer and inlet tube for carbon dioxide. The mixture is heated to 120 ° C while passing a light stream of carbon dioxide. The conversion is monitored by gas chromatography at regular intervals. After one hour the reaction is complete with a 100% conversion. By distillation the title product is obtained with a yield of 90%.

EXAMPLE 2

4-methacryloyloxinethyl-1 .3-dioxolan-2-one

Operating as described in Example 1 but using 20 g of glycidyl methacrylate in 50 g of a mixture 1/1 by weight of TBAB and TBAI, the title product is obtained (after 1 hour: 90% conversion; 88% yield).

EXAMPLE 3

4-benzyl-1,3-dioxolan-2-one

Operating as described in Example 1 but using 10 g of benzyloxirane in 20 g of TBAB, the title product is obtained (after 4 hours: 100% conversion).

EXAMPLE 4

4-ethyl-1,3-dioxolan-2-one

Operating as described in Example 1 but using 10 g of ethyloxirane in 20 g of TBAB, the title product is obtained (after 5 hours: 90% conversion).

EXAMPLE 5

4-isobutyloxymethyl-1,3-dioxolan-2-one

Operating as described in Example 1 but using 20 g of glycidyl isobutyl ether in 30 g of a mixture 1/1 by weight of TBAB and TBAI, the title product is obtained (after 2 hours: 95% conversion; 90% yield) .

EXAMPLE 6

4-phenyl-1,3-dioxolan-2-one

Operating as described in Example 5 but using 20 g of phenyloxirane, the title product is obtained (after 4 hours: conversion EXAMPLE 7

4-n-hexyl-1,3-dioxolan-2-one

Operating as described in Example 6 but using 20 g of nesiloxirane, the title product is obtained (after 8 hours: 97% conversion; 80% yield).

Claims (9)

CLAIMS 1. Process for the preparation of a variously substituted 1,3-dioxolan-2-one of formula (I) wherein R is equal to hydrogen or represents from 1 to 4 substituents that are the same or different from each other, which includes - reacting an epoxide of formula (II) where R is defined as above, with carbon dioxide (CO2), at atmospheric pressure in a solvent selected from tetrabutylammonium bromide (TBAB) and a mixture of tetrabutylammonium bromide (TBAB) and tetrabutylammonium iodide (TBAI), at a higher temperature or equal to 1 10 ° C, e - optionally isolate the 1,3-dioxolan-2-one of formula (I) thus obtained. 2. Process according to claim 1, wherein the reaction temperature is greater than or equal to 120 ° C. 3. Process according to claim 2, wherein the reaction temperature is about 120 ° C. 4. Process according to claim 1, wherein the product (I) is isolated by distillation. 5. A process according to claim 1, wherein the TBAB / TBAI solvent mixture is about 1/1 by weight. 6. Process according to claim 1, wherein R represents one or two substituents, independently selected from aryls and alkyls, optionally substituted with ester or ether radicals. 7. Process according to claim 5, wherein R is selected from phenyl-; benzyl-; (C1-C6) alkyl-; ; wherein R 'is selected from is selected from phenyl, benzyl and (C 1 -C6) alkyl; Falchile being linear or branched. 8. Process according to claim 1, wherein R represents a single substituent. 9. Process according to claim 1, wherein 1,3-dioxolan-2-one is selected from 4-phenoxymethyl-1,3-dioxolan-2-one, 4-methacryloxyloxymethyl-1,3-dioxolan-2- one, 4-benzyl-1,3-dioxolan-2-one, 4-ethyl-1, 3-dioxolan-2-one, 4-isobutyloxymethyl-1,3-dioxolan-2-one, 4-phenyl-1, 3-dioxolan-2-one and 4-n-hexyl-1,3-dioxolan-2-one.