Process for preparing imidazopyridine derivatives

Claim 1

Process for preparing an imidazopyridine derivative of formula: ##STR12## wherein R 1 is an alkyl, cycloalkyl, aryl or aralkyl group or is a heterocyclic radical, R 2 and R 4 are identical or different and are hydrogen, a hydroxy, a cyano, alkyl, cycloalkyl, aryl or aralkyl group or are an alkanoyl or an alkoxy-carbonyl group, and R 3 is hydrogen, an alkyl, aryl or aralkyl group or a halogen atom, comprising reacting a nitrile of formula: R.sub.1 CN II wherein R 1 is as defined above, with a thiol of formula: R.sub.5 SH III wherein R 5 is alkyl, aryl or aralkyl, in the presence of a hydrogen halide to give a thioimidate hydrohalide of formula: ##STR13## wherein R 1 and R 5 are as defined above and X is a halogen atom, reacting the thioimidate hydrohalide of formula IV with aminoacetonitrile to give an amidine of formula: ##STR14## wherein R 1 and X are as defined above, and finally cyclizing the amidine of formula V in the presence of a base with a 1,3-dicarbonyl compound of formula: ##STR15## wherein R 3 is as defined above and R 6 and R 7 are identical or different and are hydrogen or alkyl, cyano, cycloalkyl, alkanoyl, aryl, aralkyl, alkoxy or alkoxycarbonyl, to give the final product of formula I.