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Chemical process and intermediates used therein

  • US 5,334,718 A
  • Filed: 01/25/1993
  • Issued: 08/02/1994
  • Est. Priority Date: 01/28/1992
  • Status: Expired due to Fees
First Claim
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1. A process for the manufacture of an imidazo [4,5-b]pyridine of the formula I ##STR6## or a physiologically acceptable salt thereof, wherein R1 is (1-6C)alkyl;

  • R2 is hydrogen or halogeno; and

    R3 and R4 are selected from hydrogen, halogeno, (1-6C)alkyl, (1-6C)alkoxy, hydroxymethyl and hydroxy;

    which is characterised in that a compound of the formula II ##STR7## wherein P1 is an electron-deficient phenyl group or is a pyridyl or pyrimidyl group, is reacted with a base selected from an alkali metal hydroxide, (1-12C)alkanolate, (1-12C)alkanethiolate, phenolate, thiophenolate and diphenylphosphide, wherein any phenyl ring of the latter three groups may optionally bear a (1-4C)alkyl, (1-4C)alkoxy or halogeno substituent;

    whereafter;

    when a physiologically acceptable salt of a compound of formula I is required, it is obtained by reaction with the appropriate acid or base affording a physiologically acceptable ion, or by any other conventional salt formation procedure; and

    when an optically active form of a compound of formula I is required, the process is carried out with an optically active form of the starting material of formula II, or a racemic form of a compound of formula I is resolved using a conventional procedure; and

    wherein R1, R2, R3, R4 and P1 have any of the meanings defined above.

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