Methods of making compounds and mixtures having antidegradant and antifatigue efficacy
Methods of making antidegradant compounds are disclosed in which a p-phenylenediamine is reacted with a dicarbonyl to thereby obtain a diimine, which is reduced to obtain mixtures comprising the antidegradant compound.
1. A method of making an antidegradant compound, the method comprising:
reacting a p-phenylenediamine corresponding to formula IV:
wherein X is selected from the group consisting of alkyl, aryl, alkylaryl groups and hydrogen;
with a dicarbonyl corresponding to formula II:
wherein R 1 and R 3 are each independently selected from the group consisting of alkyl, aryl, alkylaryl groups and hydrogen, and wherein R 1 and R 3 may optionally be bridged by a polymethylene group;
to thereby obtain a diimine; and
reducing the diimine to thereby obtain a mixture comprising the antidegradant compound according to formula I:
wherein each X is independently selected from the group consisting of alkyl, aryl, alkylaryl groups and hydrogen;
wherein R 1 and R 3 are each independently selected from the group consisting of alkyl, aryl, alkylaryl groups and hydrogen; and
wherein R 1 and R 3 may optionally be bridged by a polymethylene group to form a cycloalkyl.
2. The method of claim 1 , wherein the p-phenylenediamine comprises 4-amino-p-phenylene diamine.
3. The method of claim 1 , wherein the dicarbonyl comprises diacetyl.
4. The method of claim 1 , wherein the dicarbonyl comprises diacetyl, and wherein the p-phenylenediamine and the dicarbonyl are reacted in the presence of a solvent and an acid catalyst.
5. The method of claim 4 , wherein the acid catalyst comprises one or more of formic acid, acetic acid, propionic acid, p-toluenesulfonic acid, camphorsulfonic acid, hydrochloric acid, sulfuric acid, and phosphoric acid.
6. The method of claim 1 , wherein the diimine is reduced by hydrogenation in the presence of: (a) a solvent, (b) a homogeneous or heterogeneous metal catalyst, and (c) one or more of hydrogen gas, formic acid, or a formic acid salt.
7. The method of claim 6 , wherein the solvent comprises methylisobutylketone and the mixture comprising the antidegradant compound further comprises N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine.
8. The method of claim 6 , wherein the solvent comprises acetone and the mixture comprising the antidegradant compound further comprises N-isopropyl-N′-phenyl-p-phenylenediamine.
9. The method of claim 1 , wherein the diimine is reduced by a reducing agent comprising di-isobutyl aluminum hydride and lithium aluminum hydride in the presence of one or more of diethyl ether, tetrahydrofuran, or tert-butylmethyl ether.
10. The method of claim 1 , wherein the diimine is reduced by a reducing agent comprising sodium borohydride, lithium borohydride, and sodium cyanoborohydride in the presence of one or more of methanol, ethanol, and isopropanol.
11. The method of claim 1 , wherein the step of reacting the p-phenylenediamine with the dicarbonyl and the step of reducing the diimine thereby obtained are carried out in sequence, with optional isolation of the intermediate diimine compound.
12. The method of claim 1 , wherein the step of reacting the p-phenylenediamine with the dicarbonyl and the step of reducing the diimine thereby obtained are carried out simultaneously in the same reaction mixture.
13. The method of claim 1 , wherein the diimine obtained comprises (N,N′)—N,N′-(butane-2,3-diylidene)bis(N-phenylbenzene-1,4-diamine).