Chemical process and intermediates used therein
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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Abstract
The invention provides a novel chemical process for the manufacture of certain imidazo[4,5-b]pyridine derivatives of the formula I wherein R1, R2, R3 and R4 have the various meanings defined herein, and their non-toxic salts, which are angiotensin II inhibitors. The process involves the removal of an electron-deficient phenyl group or a pyridyl or pyrimidyl group from a compound of the formula II as defined herein. Certain of the intermediates are novel and are provided as a further feature of the invention.
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11 Claims
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- R2 is hydrogen or halogeno; and
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10. A process as claimed in claim i for the preparation of an imidazo[4,5-b]pyridine of the formula I selected from 2-butyl-3-[(2'"'"'-(1H-tetrazol-5-yl)biphenyl-4-yl)-methyl]-3H-imidazo-[4,5-b]pyridine and 2-ethyl-5,7-dimethyl-3-[(2'"'"'-(lH-tetrazol-5-yl)biphenyl-4yl)methyl]-3H-imidazo[4,5-b]pyridine), or of a physiologically acceptable salt thereof.
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11. A compound of the formula II ##STR8## in either a racemic or optically active form;
- wherein P1 is an electron-deficient phenyl group or is a pyridyl or pyrimidyl group; and
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.
- wherein P1 is an electron-deficient phenyl group or is a pyridyl or pyrimidyl group; and
Specification