Process for the preparation of a mixture of alkylated...

Details Process for the preparation of a mixture of alkylated... Process for the preparation of a mixture of alkylated...

2000-07-05

2002-06-18

Shah, Mukund J. (Department: 1624)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C544S031000, C544S036000, C544S044000

Reexamination Certificate

active

06407231

ABSTRACT:

The present invention relates to a novel, technically advantageous process for the preparation of a mixture of alkylated phenothiazines and diphenylamines.
Additives are added to improve the performance properties of numerous organic products having a wide range of application in the technology, e.g. lubricants, hydraulic fluids, metal working fluids, fuels or polymers.
Liquid mixtures of aminic antioxidants have been used for some time in particular in lubricating oils for combustion engines. It is known from U.S. Pat. No. 2,433,658 to prepare phenothiazine by reacting diphenylamine with sulfur. EP-A-0 475 904 describes the preparation of a substance mixture of alkylated phenothiazines by reacting alkylated diphenylamines with sulfur. The alkylated diphenylamine mixture is prepared beforehand by the process described in EP-A-0 149 422 by reacting diphenylamine with an olefin as alkylating agent, e.g. diisobutylene. This alkylation process is not very selective since mixtures with differently alkylated products are obtained, e.g. mixtures of 2,2′-, 2,4′-, 4-, 4,4′- and 2,4,4′-alkylated diphenylamines. The subsequent reaction of such mixtures by the process described in EP-A-0 475 904 yields mixtures of correspondingly alkylated diphenylamines and phenothiazines of low selectivity.
This invention has for its general object to provide mixtures of alkylated diphenylamines and phenothiazines with increased selectivity of the alkylation in 3- and 7-position. EP-A-0 659 749 describes the selective alkylation of a mixture of diphenylamines and phenothiazines with olefins, e.g. diisobutylene. However, this process is not advantageous because the synthesis requires that mixtures of diphenylamine and phenothiazine are already present as starting material.
This invention has the more restricted object of preparing—starting from pure diphenylamine or naphthylamine as sole starting material—mixtures of alkylated diphenylamines and phenothiazines having increased selectivity of the alkylation in 3- and 7-position.
This object is achieved by this invention, which relates to a so-called one-pot process for the preparation of a mixture of alkylated phenothiazines and diphenylamines.
This invention relates to a process for the preparation of a mixture comprising alkylated phenothiazines of formula:
and correspondingly substituted diphenylamines of formula:
wherein R
1
and R
2
are hydrogen or together are the group:
one of R
3
and R
3′
is hydrogen and the other is C
2
-C
30
alkyl, cyclo-C
5
-C
12
alkyl-C
2
14
4
alkyl &agr;-C
1
-C
2
alkylbenzyl or &agr;,&agr;-dimethylbenzyl;
or both R
3
and R
3′
are C
2
-C
30
alkyl, cyclo-C
5
-C
12
alkyl-C
2
-C
4
alkyl, &agr;-C
1
-C
2
akylbenzyl or &agr;,&agr;-dimethylbenzyl, if R
1
and R
2
are hydrogen; or
R
3
is hydrogen and R
3′
is C
2
-C
30
alkyl, cyclo-C
5
-C
12
alkyl-C
2
-C
4
alkyl, &agr;-C
1
-C
2
alkylbenzyl or &agr;,&agr;-dimethylbenzyl, if R
1
and R
2
together are the group A,
which process comprises reacting a diphenylamine of formula:
wherein R
1
and R
2
have the meanings given for formula 1, with elemental sulfur in the presence of a condensation catalyst selected from the group consisting of iodine, aluminium bromide, aluminium chloride, iron-III-chloride, antimonium chloride, copper iodide and sulfur iodide and reacting the obtainable substance mixture of diphenylamine (III) and phenothiazine of formula:
wherein R
1
and R
2
have the meanings cited for formula I, with an olefin of formula:
containing the number of the carbon atoms in R
3
or R
3′
, wherein one of R
3
a
, R
3
b
and R
3
c
is cyclo-C
5
-C
12
alkyl or phenyl and the other radicals are hydrogen or methyl, or R
3
a
, R
3
b
and R
3
c
are each independently of one another hydrogen or C
1
-C
28
alkyl, in situ in the presence of an acid catalyst and isolating the mixture of the compounds (I) and (II).
In a particularly preferred embodiment of this invention, the two process steps are carried out as one-pot processes. R
3
and R
3′
defined as C
2
-C
30
alkyl are preferably C
2
-C
20
alkyl, more preferably C
4
-C
12
alkyl, e.g. straight-chain or branched (from 3 carbon atoms) alkyl, typically ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 2-ethyl-n-butyl, 1-methyl-n-pentyl, 1,3-dimethylbutyl, n-heptyl, isoheptyl, 1,1,3,3-tetramethylbutyl, 1-methylhexyl, 2-methylhexyl, n-octyl, isooctyl, 1,4,4-trimethyl-2-pentyl, 1-methylheptyl, n-nonyl, 1,1,3-tri-methylhexyl, n-decyl, n-undecyl, n-dodecyl, 1-methylundecyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl or n-eicosyl.
Cyclo-C
5
-C
12
alkyl-C
2
-C
4
alkyl is, for example, cyclopentyl-1,1-ethyl, cyclohexyl-1,1-ethyl, cyclopentyl-1,2-ethyl, cyclohexyl-1,2-ethyl, cyclopentyl-1,2-propyl or cyclohexyl-1,2-propyl.
&agr;-C
1
-C
2
alkylbenzyl is, for example, methylbenzyl (=1,1-phenethyl).
In a preferred embodiment of this process the reaction is carried out using about 0.5 to 200 mol % of elemental sulfur in the presence of about 0.001 to 10 mol % of the condensation catalyst selected from the group consisting of iodine, aluminium bromide, aluminium chloride, iron-III-chloride, antimonium chloride, copper iodide and sulfur iodide in the temperature range from about 80° to 250° C.
In another preferred embodiment of the process, the reaction is carried out using 10 to 150 mol %, preferably 15 to 100 mol %, of elemental sulfur.
The preferred embodiments of this process include the reaction with 0.001 to 1.0 mol % of the condensation catalyst.
In a particularly preferred embodiment of this process the reaction is carried out using 0.001 to 0.01 mol % of elemental iodine.
The reaction temperature is in the range from about 800 to 250° C., preferably from 120° to 190° C. In the course of the reaction, hydrogen sulfide (H
2
S) is formed. Owing to its toxicity and bad smell this is removed from the reaction vessel and led into an aqueous alkali hydroxide solution. Alkali sulfide forms then which can be easily disposed of.
In the first process step, the reaction time can be e.g. from about 1 to 15 hours, a reaction time of 2 to 4 hours being useful and one of about 1 to 2 hours being preferred.
The reaction can be carried out by adding the diphenylamine (III), where appropriate dissolved in one of the cited solvents, to the sulfur and the catalyst. This mixture is heated, with stirring, to the cited temperature. The course of the reaction can be observed via the formation of hydrogen sulfide. After the cited reaction time, or if analysis no longer shows any free sulfur, the reaction of the first process step can be terminated, e.g. by cooling the reaction vessel to about 100° C.
The mixture of the compounds (III) and (IV) can be used in the second process step in a molar ratio of about 95:5 to 5:95, preferably of 30:70 to 70:30.
In a preferred variant of the process, the compounds (III) and compounds (IV) are used in the second process step in a molar ratio of about 30:70 to 5:95, particularly preferably of 20:80 to 10:90.
The olefin (V) is used in the second process step in a molar ratio of about 0.5 to 4.0 mol, preferably of 1.0 to 3.0 mol, more preferably of 1.0 to 2.0 mol, per mol of the mixtures of the compounds (III) and (IV).
The number of the carbon atoms in the olefin (V) corresponds to the number of carbon atoms in R
3
or R
3′
. If R
3
or R
3′
is tert-octyl or 1,4,4-trimethyl-2-pentyl, diisobutylene is used as olefin (V). Other suitable olefins are, for example, ethylene, propylene, isobutylene, 2-methyl-pentene, tripropylene, tetrapropylene, styrene or methylstyrene.
Suitable acid catalysts are proton donors (so-called Brønsted acids), electron acceptor compounds (so-called Lewis acids), cation exchanger resins, alumosilicates or naturally occurring or modified sheet silicates.
Suitable proton donors (so-called Brønsted acids) are, for example, salt-forming inorganic or organic acids, e.g. mineral acids such as hydrochloric acid, sulfuric acid or phosphoric acid, carboxylic acids, e.g. acetic aci

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