Process for preparing S,S′-dialkyldithiocarbonate from dialkyl disulfide
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.
1. A process for preparing a S,S′-dialkyldithiocarbonate, comprising:
reacting in the presence of carbon monoxide:
a dialkyl disulfide chosen from formula (I) below, and mixtures thereof:
R 1 —S—S—R 2
wherein R 1 and R 2 , which may be identical or different, are a C 1 -C 12 alkyl group,
a catalyst comprising a metal chosen from nickel, palladium and platinum,
and
optionally in the presence of a solvent or of a mixture of solvents.
2. The process according to claim 1 , wherein R 1 and R 2 are identical and are a C 1 -C 4 alkyl group.
3. The process according to claim 1 , wherein the catalyst comprises palladium.
4. The process according to claim 1 , wherein the number of moles of the catalyst is between 0.1 and 3 mol %, relative to the total number of moles of the dialkyl disulfide.
5. The process according to claim 1 , wherein the reacting step is carried out under a total carbon monoxide pressure of between 1 and 20 MPa.
6. The process according to claim 1 , wherein the reacting step further comprises the addition, to the reaction medium, of at least one additional ligand.
7. The process according to claim 6 , 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.
8. The process according to claim 6 , wherein the number of moles of the additional ligand(s) is between 0.1 and 6 mol %, relative to the total number of moles of the dialkyl disulfide.
9. The process according to claim 2 , wherein R 1 and R 2 are each a methyl group.
10. The process according to claim 3 , wherein the catalyst is tetrakis(triphenylphosphine)palladium.