Method for preparing dialkyl dicarbonates using amine oxides

Abstract

The present invention relates to a method for preparing dialkyl dicarbonates from the corresponding alkyl chloroformates using specific amine oxides as catalysts.

Claims

1. A method for preparing dialkyl dicarbonates, comprising reacting an alkyl haloformate with at least one alkali metal hydroxide, alkaline earth metal hydroxide and/or carbonate in the presence of at least one organic solvent immiscible with water and in the presence of a catalyst, wherein the catalyst is at least one compound of the formula (I) ##STR00004## in which R.sup.1 and R.sup.2 is straight-chain or branched C.sub.1-C.sub.6-alkyl, R.sup.3 is straight-chain or branched C.sub.10-C.sub.22-alkyl, wherein R.sup.1 and R.sup.2 may be the same or different.

2. The method according to claim 1, wherein R.sup.3 is selected from the group of straight-chain or branched dodecanyl, undecanyl, tridecanyl, tetradecanyl, pentadecanyl, hexadecanyl, heptadecanyl, octadecanyl, nonadecanyl, eicosanyl, icosanyl, heneicosanyl and dodoconyl.

3. The method according to claim 1, wherein R.sup.3 is selected from the group of straight-chain or branched C.sub.10-, C.sub.11-, C.sub.12-, C.sub.13-, C.sub.14-, C.sub.15-, C.sub.16-, C.sub.17-, and C.sub.18-alkyl.

4. The method according to claim 1, wherein R.sup.1 and R.sup.2 are selected from the group of methyl, ethyl, n-propyl, s-propyl, n-butyl, s-butyl, isobutyl and t-butyl and R.sup.3 is straight-chain or branched C.sub.10-C.sub.18-alkyl.

5. The method according to claim 1, wherein R.sup.1 and R.sup.2 are methyl and R.sup.3 is C.sub.10-C.sub.16-alkyl.

6. The method according to claim 1, wherein R.sup.1 and R.sup.2 are methyl and R.sup.3 is selected from the group of dodecanyl, tetradecanyl, and hexadecanyl.

7. The method according to claim 1, wherein R.sup.3 is selected from the group of straight-chain or branched C.sub.12-, C.sub.14- and C.sub.16-alkyl and R.sup.1 and R.sup.2 are methyl and wherein the content of the compound where R.sup.3=C.sub.12-alkyl is from 60% by weight to 80% by weight and the content of the compound where R.sup.3=C.sub.14-alkyl is from 19% by weight to 30% by weight and the content of the compound where R.sup.3=C.sub.16-alkyl is from 1% by weight to 10% by weight, based on the total weight of the compound of the formula (I).

8. The method according to claim 1, wherein the dialkyl dicarbonates are of formula (II) ##STR00005## in which R.sup.4 is straight-chain or branched C.sub.1-C.sub.20-alkyl, and are formed by reacting alkyl haloformates of formula (III) ##STR00006## in which Hal is halogen and R.sup.4 is straight-chain or branched C.sub.1-C.sub.20-alkyl.

9. The method according to claim 8, wherein R.sup.4 is methyl, ethyl, n-propyl, isopropyl, or n-butyl or isobutyl.

10. The method according to claim 1, wherein the alkali metal hydroxides or alkaline earth metal hydroxides and/or carbonates are in the form of aqueous solutions.

11. The method according to claim 1, wherein the at least one organic solvent immiscible with water is selected from the group of aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, dialkyl carbonates, ethers and esters immiscible with water.

12. The method according to claim 1, wherein the catalyst is present in the amount of 0.1 to 7 mol %, based on the haloformate.

13. The method according to claim 1, wherein the reaction is carried out at a temperature of 15 C. and 19 C. (at standard pressure).

14. The method according to claim 1, wherein the reaction is carried out in a continuous mode of operation.

15. The method according to claim 1, further comprising, after completion of the reaction whereby a reaction mixture is formed, phase separating the dialkyl dicarbonate whereby an organic phase is formed and subsequently performing a multi-stage distillation of the organic phase.

Description

EXAMPLES

Example 1

(1) A mixture of 18.87 g (0.2 mol) of methyl chloroformate (MC) and 14.83 g of toluene is initially charged in a reaction vessel and 3.57 g of Barlox 12 (Lonza, Basel) (0.0045 mol) ((30% by weight solution of 70% lauryldimethyldiamine oxide (amine oxide of the formula (I) where R.sup.1 and R.sup.2=methyl, R.sup.3=C.sub.12-alkyl), 26% myristamine oxide (amine oxide of the formula (I) where R.sup.1 and R.sup.2=methyl, R.sup.3=C.sub.14-alkyl and 4% hexadecanyldimethylamine oxide (amine oxide of the formula (I) where R.sup.1 and R.sup.2=methyl, R.sup.3=C.sub.16-alkyl) in water) and 62.73 g of ca. 14% NaOH (0.22 mol) are then introduced.

(2) This mixture is reacted with vigorous stirring at 17 C. After ca. 20 min, the phases were separated.

(3) The crude yield of dimethyl dicarbonate is ca. 95% based on the amount of MC used.

Comparative Example 1 Using a Tertiary Amine as Catalyst

(4) The present example is already known in similar form from EP 1747185 A (Example 3).

(5) A mixture of 20.41 g (0.22 mol) of MC and 14.78 g of toluene is initially charged in a reaction vessel and then 0.54 g (0.0015 mol) of Alamine 308 (triisooctylamine) and 64.27 g of ca. 14% NaOH (0.22 mol) are introduced.

(6) This mixture is reacted with vigorous stirring at 12 C. After ca. 20 min, the phases were separated.

(7) The crude yield of dimethyl dicarbonate is ca. 91% based on the amount of MC used.