Process for the reduction of a tertiary phosphine oxide to the corresponding tertiary phosphine in the presence of a catalyst and use of a tertiary phosphine for reducing a tertiary phosphine oxide in the presence of a catalyst
A process for the conversion of a tertiary phosphine oxide to the corresponding tertiary phosphine includes reacting the tertiary phosphine oxide with a reducing tertiary phosphine, in the presence of a catalyst that catalyzes the conversion.
1. A process for reducing a tertiary phosphine oxide to a corresponding tertiary phosphine, comprising reacting said tertiary phosphine oxide with a reducing tertiary phosphine, in the presence of a halogen catalyst selected from the group consisting of fluorine (F 2 ), chlorine (Cl 2 ), bromine (Br 2 ), iodine I 2 ), cyanuric chloride, halomethane, and phosphine dihalide.
2. The process according to claim 1 , wherein
(i) the tertiary phosphine oxide is of formula (I)
wherein, each of R 1 , R 2 and R 3 is independently selected from the group consisting of substituted or unsubstituted, branched or linear hydrocarbyl; and substituted or unsubstituted carbocyclyl or heterocyclyl;
A is a linking moiety; and
m is an integer of from 0 to 2;
(ii) the corresponding tertiary phosphine is of formula (III)
wherein R 1 , R 2 , R 3 , A and m are as defined herein above; and
(iii) the reducing tertiary phosphine is of formula (II)
wherein, each of R 4 , R 5 and R 6 is independently selected from the group consisting of substituted or unsubstituted, branched or linear hydrocarbyl; and substituted or unsubstituted, aliphatic or aromatic carbocyclyl or heterocyclyl;
B is a linking moiety; and
n is an integer of from 0 to 2.
3. The process according to claim 2 , wherein each of A and B is independently selected from substituted or unsubstituted hydrocarbylene, substituted or unsubstituted monocyclic or polycyclic carbocyclylene, substituted or unsubstituted monocyclic or polycyclic heterocyclylene, and substituted or unsubstituted metallocenylene.
4. The process according to claim 1 , wherein the halogen catalyst is a tetrahalomethane.
5. The process according to claim 1 , wherein the process is performed under solvent-free conditions or in an anhydrous aprotic solvent.
6. The process according to claim 5 , wherein the anhydrous aprotic solvent is selected from the group consisting of tetrahydrofuran, acetonitrile, diethylether, propionitrile, toluene, ethyl acetate, and mixtures thereof.
7. The process according to claim 1 , wherein the reducing tertiary phosphine is added to the reaction mixture at a molar ratio of the phosphine function(s) of the reducing tertiary phosphine to the phosphine oxide function(s) of the tertiary phosphine oxide of at least 1.
8. The process according to claim 1 , wherein the basicity of the reducing tertiary phosphine is greater than the basicity of the product tertiary phosphine.
9. The process according to claim 1 , wherein the tertiary phosphine oxide to be reduced is attached to a solid support.
10. The process according to claim 1 , wherein the reducing tertiary phosphine is attached to a solid support.
11. The process according to claim 2 , wherein the process is performed under solvent-free conditions or in an anhydrous aprotic solvent.
12. The process according to claim 3 , wherein the process is performed under solvent-free conditions or in an anhydrous aprotic solvent.
13. The process according to claim 4 , wherein the process is performed under solvent-free conditions or in an anhydrous aprotic solvent.
14. The process according to claim 1 , wherein the halogen catalyst is Br 2 or I 2 .
15. The process according to claim 4 , wherein the tetrahalomethane is selected from the group consisting of tetrachloromethane, tetrabromomethane, tetraiodomethane, and tetrafluoromethane.
16. The process according to claim 1 , wherein the halogen catalyst is tetrachloromethane.
17. The process according to claim 1 , wherein the catalyst is a tertiary phosphine dihalide.
18. The process according to claim 17 , wherein the tertiary phosphine dihalide is selected from the group consisting of triphenylphosphine dichloride, triphenylphosphine dibromide, triphenylphosphine diiodide, and triphenylphosphine difluoride.
19. The process according to claim 1 , wherein the reaction is carried out at ambient temperatures.