Process for preparing unsymmetric OCO pincer ligands from the group of the M-terphenyl compounds
The present invention relates to a process for preparing unsymmetric compounds from the group of the m-terphenyls which can be used as unsymmetric OCO pincer ligands, comprising the process steps of a) reacting a first substituted or unsubstituted phenol with a 1,3-disubstituted arene which may likewise be substituted in the 2 and 5 positions to obtain a phenol-arene coupling product and b) optionally protecting the OH group of the phenol-arene coupling product with a protecting group to obtain a protected phenol-arene coupling product, and c) reacting the phenol-arene coupling product from a) or b) with a second substituted or unsubstituted phenol to obtain an unsymmetric m-terphenyl, with the proviso that the first phenol and the second phenol have different substitution, characterized in that at least one of process steps a) and c) is conducted as an electrochemical process step.
1. A process for preparing unsymmetric compounds from the group of the m-terphenyls, comprising the process steps of
a) reacting a first substituted or unsubstituted phenol with a 1,3-disubstituted arene which may be substituted in the 2 and 5 positions to obtain a phenol-arene coupling product and
b) optionally protecting the OH group of the phenol-arene coupling product with a protecting group to obtain a protected phenol-arene coupling product,
c) reacting the phenol-arene coupling product from a) or b) with a second substituted or unsubstituted phenol to obtain an unsymmetric m-terphenyl,
with the proviso that the first phenol and the second phenol have different substitution, wherein
at least one of process steps a) and c) is conducted as an electrochemical process step, and the electrochemical process step comprises:
mixing at least one solvent and at least one conductive salt to form a mixture;
adding compounds to be converted to the mixture to form a reaction mixture:
introducing at least two electrodes into the reaction mixture; and
applying a voltage to the electrodes.
2. The process according to claim 1 , wherein
both process steps a) and c) are conducted as electrochemical process steps.
3. The process according to claim 1 ,
wherein the electrochemical process step further comprises:
adding the phenol in molar deficiency relative to the other component to be converted,
converting the components to the corresponding coupling products,
switching off the voltage, and optionally
isolating and/or purifying the reaction product.
4. The process according to claim 1 , wherein
the molar ratio of the 1,3-disubstituted arene which may be substituted in the 2 and 5 positions to the first substituted or unsubstituted phenol is in the range from 1.5:1 to 6:1.
5. The process according to claim 1 , wherein
the molar ratio of the phenol-arene coupling product to the second phenol is in the range from 1.5:1 to 6:1.
6. The process according to claim 1 , wherein
the first substituted or unsubstituted phenol corresponds to the formula (A)
the second substituted or unsubstituted phenol to the formula (A′)
and the 1,3-disubstituted arene which may be substituted in the 2 and 5 positions to the formula (B)
and R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 10 and R 12 are each independently selected from the group consisting of hydrogen, (C 1 -C 12 )-alkyl, O—(C 1 -C 12 )-alkyl, (C 6 -C 20 )-aryl, O—(C 6 -C 20 )-aryl and halogen,
in which R 9 and R 11 are each independently selected from the group consisting of (C 1 -C 12 )-alkyl, O—(C 1 -C 12 )-alkyl, (C 6 -C 20 )-aryl, O—(C 6 -C 20 )-aryl and halogen,
and in which at least one pair among the R 1 /R 5 , R 2 /R 6 , R 3 /R 7 and R 4 /R 8 pairs consists of different radicals.
7. The process according to claim 6 , where R 10 and R 12 are identical.
8. The process according to claim 1 ,
wherein the at least one solvent is selected from the group consisting of acetonitrile, propylene carbonate, methyl carbonate, nitromethane, ethylene glycol dimethyl ether, methanesulphonic acid, benzene, toluene, water, methanol, ethanol, propanol, isopropanol, halogenated solvents, halogenated or non-halogenated acids, and mixtures thereof.
9. The process according to claim 8 ,
wherein the solvent is methanol, formic acid, trifluoroacetic acid, hexafluoroisopropanol or mixtures thereof.
10. The process according to claim 1 , wherein
the reaction is conducted without the use of organic oxidizing agents.
11. The process according to claim 1 ,
wherein the at least one conductive salt is selected from the group consisting of tetra(C 1 -C 6 -alkyl)ammonium and 1,3-di(C 1 -C 6 -alkyl)imidazolium salts, with the proviso that the alkyl groups may be halogen-substituted.
12. The process according to claim 11 , wherein
the counterions of the conductive salts are selected from the group consisting of arsenate, sulphate, hydrogensulphate, alkylsulphate, alkylphosphate, perchlorate, fluoride, arylsulphate, hexafluorophosphate, and tetrafluoroborate.
13. The process according to claim 1 , wherein the conductive salt is selected from the group consisting of quaternary ammonium borates, ammonium fluoroalkylphosphates, ammonium fluoroalkylarsenates, ammonium trifluoromethylsulphonates, ammonium bis(fluoromethanesulphon)imides, ammonium tris(fluoromethanesulphonyl)methides, methyltributylammonium methylsulphate, methyltriethylammonium methylsulphate, tetrabutylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, lithium hexafluorophosphate, and tetraethylammonium tetrafluoroborate.
14. The process of claim 4 , wherein the molar ratio of the 1,3-disubstituted arene which may be substituted in the 2 and 5 positions to the first substituted or unsubstituted phenol is in the range from 2:1 to 3:1.
15. The process of claim 5 , wherein molar ratio of the phenol-arene coupling product to the second phenol is in the range from 2:1 to 3:1.
16. The process of claim 6 , wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 10 and R 12 are each independently selected from the group consisting of hydrogen, (C 1 -C 12 )-alkyl, O—(C 1 -C 12 )-alkyl and halogen.
17. The process of claim 16 , wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 10 and R 12 are each independently selected from the group consisting of hydrogen, (C 1 -C 12 )-alkyl, and O—(C 1 -C 12 )-alkyl.
18. The process of claim 6 , wherein R 9 and R 11 are each independently selected from the group consisting of (C 1 -C 12 )-alkyl, O—(C 1 -C 12 )-alkyl, and halogen.
19. The process of claim 18 , wherein R 9 and R 11 are each independently selected from (C 1 -C 12 )-alkyl or O—(C 1 -C 12 )-alkyl.
20. The process of claim 7 , wherein R 10 and R 12 are hydrogen.
21. The process of claim 9 , wherein the solvent is methanol, hexafluoroisopropanol, or mixtures thereof.
22. The process of claim 21 , wherein the solvent is hexafluoroisopropanol.
23. The process of claim 13 , wherein the conductive salt is methyltriethylammonium methylsulphate or methyltributylammonium methylsulphate.
24. The process of claim 23 , wherein the conductive salt is methyltributylammonium methylsulphate.