Process for the formation of urethane via transcarbamation

1. A process for the formation of urethane through a transcarbamation reaction, comprising the steps of:

a) carrying out said reaction on a mixture of a carbamate, said carbamate resulting from the reaction of of an isocyanate functional group with a hydroxyl functional group, and an alcohol in the presence of an efficient catalytic amount, as catalyst for a reaction for the formation of urethane, of compounds of general formula (I):

MY 3−q [Z] q ,

wherein:

Z is the radical corresponding to the anion of a superacid for which the Hammett constant is at least equal to, or greater than, 13;

M representing a trivalent metal;

Y is a monovalent anion or anionic functional group: and

q is an integer; and

b) recovering the urethane formed in step a).

2. The process according to claim 1 , wherein:

the Hammett constant is greater than 13;

M forms a Lewis acid; and

q is between 1 and 3, including the limits.

3. The process according to claim 1 , wherein Z is of formula:

(R x )—SO 2 -ζ-

wherein:

R x is a fluorine or a radical, the carbon of which carrying the sulfonic functional group is perhalogenated, and

ζ is an oxygen or an atom from Group V, monosubstituted by an electron-withdrawing radical.

4. The process according to claim 3 ,

wherein:

ζ is an oxygen or nitrogen, monosubtituted by the electron-withdrawing radical of formula (R′ x )—SO 2 —, wherein R′ x are radicals R x .

5. The process according to claim 4 , wherein ζ is an oxygen.

6. The process according to claim 1 , wherein the transcarbamation comprises a reaction in which a urea functional group (>N—CO—N<) is converted to a carbamate functional group (>N—CO—O—).

7. The process according to claim 6 , wherein a precursor of the urethane functional group is a masked isocyanate functional group with a masking agent.

8. The process according to claim 7 , wherein the masking agent is a compound carrying a hydroxylated functional group.

9. The process according to claim 8 , wherein the compound carrying a hydroxylated functional group is a saturated alcohol with a boiling point below 150° C., phenol, oxime or hydroxyamide.

10. The process according to claim 7 , wherein the masking agent is a compound exhibiting an >NH functional group.

11. The process according to claim 10 , wherein the compound exhibiting an >NH functional group is a secondary amine or a five-membered aromatic nitrogenous ring, optionally exhibiting at least two nitrogens.

12. The process according to claim 1 , wherein said metal M is a metal not exhibiting a valency of less than 3.

13. The process according to claim 12 , wherein said metal belongs to a period greater than the fourth, optionally than the fifth, period.

14. The process according to claim 13 , wherein said metal is a lanthanide or bismuth.

15. The process according to claim 1 , wherein R x is of formula:

EWG-(CX 2 ) p -

wherein:

the X groups, which are identical or different, represent a chlorine, a fluorine or a radical of formula C n F 2n+1, with n an integer at most equal to 5, with the further proviso that at least one of the X groups is fluorine, said fluorine being carried by the carbon connected to the sulfur;

p represents an integer at most equal to 2; and

EWG represents an electron-withdrawing group inert under the conditions of the reaction.

16. The process according to claim 15 , wherein EWG has fluorine or a perfluorinated group of formula C n F 2n+1, with n an integer at most equal to 8, the total carbon number of Rf being between 1 and 15.

17. The process according to claim 1 , wherein the transcarbamation reaction of step a) is carried out at a temperature of between 100 and 200° C.

18. The process according to claim 1 , wherein the amount of catalyst is at least equal to 0.5% and at most equal to 5% as carbamate functional group equivalent.