Selective chlorination of a 1-(2-fluorophenyl)-1,2,4-triazole

  • US 5,965,742 A
  • Filed: 06/25/1998
  • Issued: 10/12/1999
  • Est. Priority Date: 12/29/1995
  • Status: Expired due to Fees
First Claim
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1. A process for the chlorination of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole (the "2-fluorophenyl compound") in the 4-position of the phenyl ring which comprisesa) adding 0.8 to 1.6 molar equivalents of chlorine to a stirred slurry of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole in a solvent selected from acetonitrile, N,N-dimethylformamide, nitromethane, and nitrobenzene, at a temperature in the range of ambient to 50°

  • C., at a rate such that the temperature does not exceed 50°

    C., and continuing the stirring at 30 to 50°

    C. for from one to ten hours;

    b) for a period of from one to six hours, while maintaining the temperature at 30 to 50°

    C., reducing the pressure in the reaction vessel so that the solvent refluxes and most of the hydrogen chloride by-product is driven off;

    c) optionally, purging the reaction vessel with nitrogen to reduce the hydrogen chloride concentration in the reaction mixture to below 1%;

    d) repeating steps a, b, and c two times;

    e) recovering 1-(4-chloro-2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole.

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