The present invention relates to an industrial process of preparing pharmaceutical compounds having the formula (I) which are useful as certain tyrosine kinase inhibitors and more particularly as c-kit and bcr-abl inhibitors. The groups R1 and R2, identical or different, represent each a hydrogen, halogen atom, an alkyl, an alkoxy, a trifluoromethyl, an amino, an alkylamino, a dialkylamino, a solubilising group; m is 0-5 and n is 0-4; the group R3 represents an aryl or an heteroaryl group as described in claims herein.