Electrochemical coupling of anilines
An electrochemical method for coupling anilines. When coupling two different anilines, the difference of the oxidation potential of the substrates is in the region of between 10 mV to 450 mV, and the aniline with the highest oxidation potential is added in excess. The method allows biaryldiamines to be electrochemically produced, and can avoid the need for multi-step syntheses using metallic reagents.
1. Electrochemical process for preparing biaryldiamines, comprising the process steps of:
a′) introducing a solvent or solvent mixture and a conductive salt into a reaction vessel,
b′) adding a first aniline having an oxidation potential |E Ox 1| to the reaction vessel,
c′) adding a second aniline having an oxidation potential |E OX 2| to the reaction vessel, to obtain a reaction solution, where: |E Ox 2|>|E Ox 1| and |E Ox 2|−|E Ox 1|=|ΔE|,
the second aniline being added in excess relative to the first aniline,
and the solvent or solvent mixture being selected such that |ΔE| is in the range from 10 mV to 450 mV,
d′) introducing two electrodes into the reaction solution,
e′) applying a voltage to the electrodes, and
f′) coupling the first aniline to the second aniline to give a biaryldiamine,
wherein the first aniline and the second aniline each has a formula independently selected from the group consisting of Ia, Ib, IIa, IIb, IIIa, IIIb, IVa, and IVb:
where the substituents R 1 to R 48 are each independently selected from the group consisting of hydrogen, (C 1 -C 12 )-alkyl, (C 1 -C 12 )-heteroalkyl, (C 4 -C 14 )-aryl, (C 4 -C 14 )-aryl-(C 1 -C 12 )-alkyl, (C 4 -C 14 )-aryl-O—(C 1 -C 12 )-alkyl, (C 3 -C 14 )-heteroaryl, (C 3 -C 14 )-heteroaryl-(C 1 -C 12 )-alkyl, (C 3 -C 12 )-cycloalkyl, (C 3 -C 12 )-cycloalkyl-(C 1 -C 12 )-alkyl, (C 3 -C 12 )-heterocycloalkyl, (C 3 -C 12 )-heterocycloalkyl-(C 1 -C 12 )-alkyl, O—(C 1 -C 12 )-alkyl, O—(C 1 -C 12 )-heteroalkyl, O—(C 4 -C 14 )-aryl, O—(C 4 -C 14 )-aryl-(C 1 -C 14 )-alkyl, O—(C 3 -C 14 )-heteroaryl, O—(C 3 -C 14 )-heteroaryl-(C 1 -C 14 )-alkyl, O—(C 3 -C 12 )-cycloalkyl, O—(C 3 -C 12 )-cycloalkyl-(C 1 -C 12 )-alkyl, O—(C 3 -C 12 )-heterocycloalkyl, O—(C 3 -C 12 )-heterocycloalkyl-(C 1 -C 12 )-alkyl, halogens, S—(C 1 -C 12 )-alkyl, S—(C 1 -C 12 )-heteroalkyl, S—(C 4 -C 14 )-aryl, S—(C 4 -C 14 )-aryl-(C 1 -C 14 )-alkyl, S—(C 3 -C 14 )-heteroaryl, S—(C 3 -C 14 )-heteroaryl-(C 1 -C 14 )-alkyl, S—(C 3 -C 12 )-cycloalkyl, S—(C 3 -C 14 )-cycloalkyl-(C 1 -C 12 )-alkyl, S—(C 3 -C 12 )-heterocycloalkyl, (C 1 -C 12 )-acyl, (C 4 -C 14 )-aroyl, (C 4 -C 14 )-aroyl, (C 4 -C 14 )-aroyl-(C 1 -C 14 )-alkyl, (C 3 -C 14 )-heteroaroyl, (C 1 -C 14 )-dialkylphosphoryl, (C 4 -C 14 )-diarylphosphoryl, (C 3 -C 12 )-alkylsulphonyl, (C 3 -C 12 )-cycloalkylsulphonyl, (C 4 -C 12 )-arylsulphonyl, (C 1 -C 12 )-alkyl-(C 4 -C 12 )-arylsulphonyl, (C 3 -C 12 )-heteroarylsulphonyl, (C═O)O—(C 1 -C 12 )-alkyl, (C═O)O—(C 1 -C 12 )-heteroalkyl, and (C═O)O—(C 4 -C 14 )-aryl,
where the alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, awl and heteroaryl groups are optionally mono- or polysubstituted.
2. Process according to claim 1 ,
wherein the second aniline is used in at least twice the amount relative to the first aniline.
3. Process according to claim 1 ,
wherein the ratio of first aniline to second aniline is in the range from 1:2 to 1:4.
4. Process according to claim 1 ,
wherein the solvent or solvent mixture is selected such that OE is in the range from 20 mV to 400 mV.
5. Process according to claim 1 ,
wherein the reaction solution is free of organic oxidizing agents.