Process for preparing 4-aminodiphenylamines

  • US 6,140,538 A
  • Filed: 02/03/1999
  • Issued: 10/31/2000
  • Est. Priority Date: 05/18/1998
  • Status: Expired
First Claim
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1. A process for preparing an optionally substituted 4-aminodiphenylamine comprising:

  • (i) reacting an optionally substituted aniline and an optionally substituted nitrobenzene in the presence of water and a base while controlling the amount of water in relation to the base so as to ensure a molar ratio of water to the base charged in the range of not less than about 4;

    1 at the start of the coupling reaction and not less than about 0.6;

    1 at the end of the coupling reaction to produce optionally substituted 4-nitrodiphenylamine and/or 4-nitrosodiphenylamine salt;

    (ii) hydrogenating the reaction product of step (i) in the presence of a hydrogenation catalyst and added water so as to ensure a molar ratio of total water to base of at least about 4;

    1 at the end of hydrogenation;

    (iii) separating the hydrogenation catalyst from the reaction mixture; and

    (iv) obtaining an aqueous phase and organic phase from the reaction mixture, separating the organic phase from the aqueous phase and isolating the optionally substituted 4-aminodiphenylamine from the organic phase.

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