Method for the preparation of a monothiocarbonate compound

Abstract

Process for the preparation of a compound with at least one monothiocarbonate group by reacting:a compound with at least one mercaptoalcohol group anda dialkylcarbonate, in the presence of a catalyst wherein the catalyst is a salt of a metal selected from group IIIb or IVb of the periodic system.

Claims

1. A process for preparing a compound having at least one monothiocarbonate group, the process comprising: reacting a compound having at least one mercaptoalcohol group, and a dialkylcarbonate, in the presence of a catalyst, wherein the catalyst is a salt of a metal selected from group IIIb or IVb of the periodic table of elements.

2. The process of claim 1, wherein the compound having the at least one monothiocarbonate group is a compound of formula I ##STR00005## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently represent hydrogen or an organic group comprising up to 50 carbon atoms, and R.sup.2 and R.sup.4 and the two carbon atoms to which R.sup.2 and R.sup.4 are bonded optionally form a ring system.

3. The process of claim 2, wherein the compound having the at least one mercaptoalcohol group is a compound of formula IIb ##STR00006## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are defined as in formula I.

4. The process of claim 1, wherein the dialkylcarbonate is a compound of formula III ##STR00007## wherein R.sup.5 and R.sup.6 each independently represent a non-aromatic hydrocarbon group comprising 1 to 10 carbon atoms or may together form an alkylene bridge comprising 2 to 9 carbon atoms.

5. The process of claim 1, wherein the compound having the at least one mercaptoalcohol group is mercaptoethanol.

6. The process of claim 4, wherein the compound of formula III is diethylcarbonate.

7. The process of claim 1, wherein the catalyst is a salt of scandium or titanium.

8. The process of claim 1, wherein an anion of the salt is a halogenide, an alcoholate or a carboxylate.

9. The process of claim 1, wherein the catalyst is titanium tetra isopropylate.

10. The process of claim 1, wherein the catalyst is a titanium-tetra alcoholate.

11. The process of claim 1, wherein a molar ratio of mercaptoalcohol groups of the compound having at least one mercaptoalcohol group to the dialkyl carbonate is 0.5:1 to 1:0.5.

12. The process according to claim 1, wherein the catalyst is present during the reacting in an amount of 0.005 to 0.05 mol per mol of the mercaptoalcohol groups of the compound having at least one mercaptoalcohol group.

13. The process according to claim 1, wherein the reacting is carried out at a temperature of from 80 to 140 C.

14. The process according to claim 1, wherein the reacting is carried out in the absence of a solvent other than the compound having at least one mercaptoalcohol group and the dialkylcarbonate.

15. The process according to claim 1, further comprising: removing an alcohol formed while reacting the compound having at least one mercaptoalcohol group and the dialkylcarbonate.

16. The process according to claim 1, further comprising: during the reacting, removing by distillation an alcohol formed from the compound having at least one mercaptoalcohol group and the dialkylcarbonate.

17. The process according to claim 1, further comprising: after the reacting, vacuum distilling the monothiocarbonate from a reaction mixture formed by reacting the compound having at least one mercaptoalcohol group and the dialkylcarbonate, wherein the monothiocarbonate obtained by the vacuum distilling has a purity of greater than 98% determined from the peak area of the monothiocarbonate peak in the gas chromatogram compared to the area of all peaks (total count).

Description

EXAMPLES

Example 1: Catalyst Titanium Tetra Isopropylate

(1) Titanium tetraisopropylate (2.27 g, 0.008 mol) was placed in a 400 mL four neck round bottom flask equipped with a magnetic stirring bar, dropping funnel, thermometer and a reflux condenser. The reaction setup was purged with inert gas, before diethylcarbonate (118.13 g, 1 mol) was added to the catalyst at room temperature. Mercaptoethanol (59.38 g, 0.76 mol) was slowly added over a period of 15 min at room temperature. The bright orange solution was heated to 110-130 C. during which ethanol is removed from the reaction mixture by distillation. The reaction was monitored via gas chromatography analysis. After about 11 h the residual amount of mercaptoethanol was lower than 1%, determined from the peak areas of the gas chromatogramm and the reaction mixture was cooled down to room temperature. Fractioned vacuum distillation of the reaction mixture at 4 mbar and a temperature of the reaction mixture of 45-90 C. resulted in a fraction of the mono thiocarbonate with a purity >98%. The yield of mono thiocarbonate was determined from the peak area of the thiocarbonate peak in the gas chromatogram compared to the area of all peaks (total count). The selectivity of mono thiocarbonate was determined from peak area of the thiocarbonate peak compared to all peaks except the peak of the starting material mercaptoethanol.

Examples 2 to 5

(2) Example 1 has been repeated, but titanium tetraisopropylate has been replaced by the same amount (in mol) of other catalysts named in the Table.

(3) TABLE-US-00001 TABLE Yield and selectivity of mono thiocarbonate from examples 1 to 6 Selectivity of thio- Yield of carbonate thio- compared to carbonate byproducts Example Catalyst [area %] [area %] 1 Titanium tetraiso- 72 87 propylate 2 Titanium 28.5 74 tetrachloride 3 Aluminium acetate 0.1 4 4 Aluminiumchloride 4.5 32 5 Toluene sulfonic 0 0 acid 6 Boric acid 0 0