Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1994-06-21
1995-07-25
Lee, Mary C.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
514367, A61K 31425, C07D27772
Patent
active
054363462
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP92/02917 filed Dec. 16, 1992.
DESCRIPTION
The present invention relates to a process for the preparation of benzothiazolyl-2-sulphenamides from 2-mercaptobenzothiazoles and primary or secondary amines in the presence of an oxidizing agent.
Sulphenamides are employed in large quantities as vulcanization accelerators.
In industry, the benzothiazolyl-2-sulphenamides are prepared from the sodium salt of 2-mercaptobenzothiazole and the corresponding amine using sodium hypochlorite or chlorine. This reaction takes place in accordance with the following reaction equation (Example: preparation of N-cyclohexylbenzothiazolyl-2-sulphenamide): ##STR1## (MBT=2-mercaptobenzothiazolyl radical)
The principal disadvantage in this reaction is the formation of large quantities of inorganic salts, causing heavy pollution of the effluent and rendering impossible the recycling of the mother liquor and of the wash water. Numerous other processes for the preparation of benzothiazolyl-2-sulphenamides have already been proposed which do not have these disadvantages.
For example, DE-C 33 25 724 describes a process in which, in accordance with the general reaction equation ##STR2## a 2-mercaptobenzothiazole or a dibenzothiazolyl 2,2'-disulphide is reacted with a primary or secondary amine, in the presence of molecular oxygen, a copper catalyst and ammonia, at temperatures of from 0.degree. to 100.degree. C. in excess amine or a mixture thereof with water as reaction medium. Using this process it has been possible to obtain, with high yields and selectivities, a highly pure product in an economic process regime (high space-time yields, recyclability of the mother liquor and continuous procedure). This Patent, to which reference is expressly made hereby, also provides a good overview of the relevant prior art.
In addition, numerous publications describe processes for the preparation of benzothiazolyl-2-sulphenamides from 2-mercaptobenzothiazole and corresponding amines using hydrogen peroxide as oxidizing agent, for example DE-A-31 27 193 which is cited in DE-C 33 25 724, and also EP-A2-0 180 869, DE-A-30 21 429 and DE-A-27 26 901. These processes using hydrogen peroxide are able to form an advantageous alternative to the abovementioned oxygen process to the extent that--unlike DE-C 33 25 724--they operate without additional auxiliaries, such as metal catalyst and ammonia, and at atmospheric pressure. However, these described processes are unsuitable for an industrial application because of the inadequate yields and/or, in some cases, the requirement for very high excesses of amine and hydrogen peroxide. These excesses in turn lead to a reduced selectivity because of secondary reactions, for example to give oxidation products of the amine, sulphites and/or sulphates.
For instance, DE-A-31 27 193 describes a process for the preparation of N-cyclohexylbenzothiazolyl-2-sulphenamide using from 1.5 to 5 mol of cyclohexylamine per mole of 2-mercaptobenzothiazole, where the oxidizing agents mentioned are sodium hypochlorite and hydrogen peroxide (Experimental Examples). In all the Experimental Examples using hydrogen peroxide (Examples 9-11), 2-mercaptobenzothiazole is reacted with three times the stoichiometric quantity of cyclohexylamine and 1.35 times the stoichiometric quantity of hydrogen peroxide; the yields indicated are 87.1%, 87.0% and 84.9%. However, a reworking of Example 9 led to a yield of only 76%.
In EP-A2-0 180 869, a process is described for the preparation of benzothiazolyl-2-sulphenamides from 2-mercaptobenzothiazole or its salts and primary amines up to a degree of conversion which is necessarily only 95%, in which process the preferred oxidizing agents are chlorine bleaching liquor, chlorine and hydrogen peroxide, and in which the only Experimental Example which relates to the use of hydrogen peroxide uses the sodium salt of 2-mercaptobenzothiazole as starting compound, prescribes the addition of sulphuric acid and sodium hydroxide solution and thus also results in the formation of so
REFERENCES:
"Cleaning Up Oxidations with H.sub.2 O.sub.2 ", given at the "International Symposium ORPEC '91", by K. M. Dear, Apr. 29-30, 1991, pp. 1-3.
Bergfeld Manfred
Eisenhuth Ludwig
Akzo Nobel N.V.
Cross Laura R.
Lee Mary C.
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