PROCESS FOR PREPARING S,S'-DIALKYLDITHIOCARBONATE FROM DIALKYL DISULFIDE

Abstract

A process for preparing an S,S′-dialkyldithiocarbonate from a dialkyl disulfide and from a particular metal catalyst, in the presence of carbon monoxide is described in addition to the use of S,S′-dialkyldithiocarbonates as reagents for the preparation of polycarbonates, compounds containing at least one urea and/or isocyanate function and compounds containing at least one thioalkyl function.

Claims

1. Process for preparing at least one S,S′-dialkyldithiocarbonate, comprising the following step (a): (a) reacting in the presence of carbon monoxide: at least one dialkyl disulfide, at least one catalyst comprising at least one metal chosen from nickel, palladium and platinum, and optionally in the presence of a solvent or of a mixture of solvents.

2. Process according to claim 1, wherein the dialkyl disulfide(s) are chosen from the dialkyl disulfides of formula (I) below, and mixtures thereof:
R.sub.1—S—S—R.sub.2 in which: R.sub.1 and R.sub.2, which may be identical or different, represent a linear or branched, saturated, C.sub.1-C.sub.12 hydrocarbon-based chain optionally containing one or more heteroatoms, which may be identical or different.

3. Process according to claim 2, wherein R.sub.1 and R.sub.2 are identical and represent a C.sub.1-C.sub.4 hydrocarbon-based chain.

4. Process according to claim 1, wherein the catalyst comprises palladium.

5. Process according to claim 1, wherein the number of moles of catalyst(s) introduced into the reaction of step (a) is between 0.1 and 3 mol %, relative to the total number of moles of dialkyl disulfide(s) introduced into the reaction of step (a).

6. Process according to claim 1, wherein the reaction according to step (a) is carried out under a total carbon monoxide pressure of between 1 and 20 MPa.

7. Process according to claim 1, wherein step (a) comprises the addition, to the reaction medium, of at least one additional ligand.

8. Process according to claim 7, wherein the additional ligand(s) are chosen from triphenylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,5-bis(diphenylphosphino)pentane, 1,1′-bis(diphenylphosphino)ferrocene, 1,3-diisopropylimidazolium tetrafluoroborate, 1,4-bis(diphenylphosphino)butane, carbon monoxide, and mixtures thereof.

9. Process according to claim 7, wherein the number of moles of additional ligand(s) introduced is between 0.1 and 6 mol %, relative to the total number of moles of dialkyl disulfide(s) introduced into the reaction of step (a).

10. Use of at least one S,S′-dialkyldithiocarbonate obtained by means of a process according to claim 1, as a reagent for the preparation of polycarbonates, of compounds comprising at least one urea and/or isocyanate function, or of compounds comprising at least one thioalkyl function.

Description

EXAMPLES

[0082] Catalyst Evaluation

[0083] The catalysts comprising at least one transition metal are evaluated in a reaction for preparing dimethyldithiocarbonate from dimethyl disulfide in a reactor and under the following conditions: [0084] Temperature: 160° C., [0085] Carbon monoxide pressure: 4 MPa.

Example 1

[0086] A solution of dimethyl disulfide (22.43 ml; 250 mmol) was diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

Example 2

[0087] Chlorotris(triphenylphosphine)rhodium (or RhCl(PPh.sub.3).sub.3) having an oxidation state (I) (2.813 g; 3.0 mmol) and triphenylphosphine (1.732 g; 6.6 mmol) were diluted into a solution of dimethyl disulfide (22.43 ml; 250 mmol) diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

Example 3

[0088] Chlorotris(triphenylphosphine)cobalt (or CoCl(PPh.sub.3).sub.3) having an oxidation state (I) (3.689 g; 4.2 mmol) and triphenylphosphine (1.732 g; 6.6 mmol) were diluted into a solution of dimethyl disulfide (22.43 ml; 250 mmol) diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

Example 4

[0089] Tetrakis(triphenylphosphine)palladium (or Pd(PPh.sub.3).sub.4) having an oxidation state (0) (3.513 g; 3.0 mmol) and triphenylphosphine (1.732 g; 6.6 mmol) were diluted into a solution of dimethyl disulfide (22.43 ml; 250 mmol) diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

[0090] The yield of the dimethyldithiocarbonate produced was determined, for each example after 3 hours, 20 hours and 40 hours of reaction, by gas chromatography on an Agilent DB1-ms 0.32 mm×60 m×5 μm column. The temperature gradient applied is 50° C. for 3 minutes, then 10° C. per minute up to 240° C., and 240° C. for 8 minutes. The detection was carried out with a thermal conductivity detector (TCD).

[0091] The results obtained are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Catalyst evaluation Examples Catalyst Yield at 3 h Yield at 20 h Yield at 40 h 1 (control) — .sup. 0% .sup. 0% .sup. 0% 2 (comparative) RhCl(PPh.sub.3).sub.3 3.8% 3.9% 3.9% 3 (comparative) CoCl(PPh.sub.3).sub.3 3.5% 3.7% 3.9% 4 (invention) Pd(PPh.sub.3).sub.4 3.9% 5.0% 5.4%

[0092] The results presented in Table 1 show that the yield of the dimethyl disulfide carbonylation reaction is improved, when the catalyst is tetrakis(triphenylphosphine)palladium having an oxidation state (0).

[0093] Evaluation of the Additional Ligands

[0094] The additional ligands 1,2-bis(diphenylphosphino)ethane (or dppe), 1,5-bis(diphenylphosphino)pentane (or dpppentane) and 1,1′-bis(diphenylphosphino)ferrocene (or dppf) are evaluated in a reaction for preparing dimethyldithiocarbonate from dimethyl disulfide and tetrakis(triphenylphosphine)palladium with an oxidation state (0) in a reactor and under the following conditions: [0095] Temperature: 160° C., [0096] Carbon monoxide pressure: 4 MPa.

Example 5

[0097] Tetrakis(triphenylphosphine)palladium having an oxidation state (0) (3.513 g; 3.0 mmol) and 1,2-bis(diphenylphosphino)ethane (3.076 g; 7.0 mmol) were diluted into a solution of dimethyl disulfide (22.43 ml; 250 mmol) diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

Example 6

[0098] Tetrakis(triphenylphosphine)palladium having an oxidation state (0) (3.513 g; 3.0 mmol) and 1,5-bis(diphenylphosphino)pentane (2.782 g; 7.0 mmol) were diluted into a solution of dimethyl disulfide (22.43 ml; 250 mmol) diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

Example 7

[0099] Tetrakis(triphenylphosphine)palladium having an oxidation state (0) (3.513 g; 3.0 mmol) and 1,1′-bis(diphenylphosphino)ferrocene (3.871 g; 7.0 mmol) were diluted into a solution of dimethyl disulfide (22.43 ml; 250 mmol) diluted in anhydrous toluene (500 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 200 rpm, brought to 160° C. and placed under a carbon monoxide pressure (4 MPa) for 40 hours.

[0100] The yield of the dimethyldithiocarbonate produced was determined, for each example after 3 hours, 20 hours and 40 hours of reaction, by gas chromatography on an Agilent DB1-ms 0.32 mm×60 m×5 μm column. The temperature gradient applied is 50° C. for 3 minutes, then 10° C. per minute up to 240° C., and 240° C. for 8 minutes. The detection was carried out with a thermal conductivity detector (TCD).

[0101] The results obtained are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Evaluation of the additional ligands Additional Examples ligand Yield at 3 h Yield at 20 h Yield at 40 h 5 (Invention) dppe 7.5% 7.8% 8.0% 6 (Invention) dpppentane 7.3% 7.8% 8.2% 7 (Invention) dppf 8.2% 8.6% 9.0%

[0102] Evaluation of the Initial Concentration of Dimethyl Disulfide

[0103] The initial concentration of dimethyl disulfide is evaluated in a reaction for preparing dimethyldithiocarbonate and in the presence of tetrakis(triphenylphosphine)palladium having an oxidation state (0) and 1,1′-bis(diphenylphosphino)ferrocene, in anhydrous toluene. The reaction is carried out in a reactor and under the following conditions: [0104] Temperature: 130° C., [0105] Carbon monoxide pressure: 15 MPa.

Example 8

[0106] Tetrakis(triphenylphosphine)palladium (or Pd(PPh.sub.3).sub.4) having an oxidation state (0) (0.35 g; 0.31 mmol) and 1,1′-bis(diphenylphosphino)ferrocene (0.5 g; 0.90 mmol) were diluted into a solution of dimethyl disulfide (26.7 ml; 300 mmol) diluted in anhydrous toluene (made up to 60 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 1200 rpm, brought to 130° C., and placed under a carbon monoxide pressure (15 MPa) for 70 hours.

Example 9

[0107] Tetrakis(triphenylphosphine)palladium (or Pd(PPh.sub.3).sub.4) having an oxidation state (0) (0.35 g; 0.31 mmol) and 1,1′-bis(diphenylphosphino)ferrocene (0.5 g; 0.90 mmol) were diluted into a solution of dimethyl disulfide (2.67 ml; 30 mmol) diluted in anhydrous toluene (made up to 60 ml). After elimination of the air using a vacuum pump, the mixture was stirred at 1200 rpm, brought to 130° C., and placed under a carbon monoxide pressure (15 MPa) for 70 hours.

[0108] For these Examples 8 and 9, the dimethyldithiocarbonate yields were determined by gas chromatography on an Agilent DB1-ms 0.32 mm×60 m×5 μm column after 24, 42 and 70 h. The temperature gradient applied is 50° C. for 3 minutes, then 10° C. per minute up to 240° C., and 240° C. for 8 minutes. The detection was carried out with a thermal conductivity detector (TCD).

[0109] The results obtained are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Evaluation of the initial concentration of dimethyl disulfide Examples Yield at 24 h Yield at 42 h Yield at 70 h 8 (Invention) 21.7% 23.3% 24.1% 9 (Invention) 57.1% 65.3% 71.9%