Chlorination of 4-(trifluoromethoxy)aniline (V) employing N-chlorosuccinimide affords the 2-chloro aniline (VI). Diazotization of aniline (VI) and subsequent quenching with potassium iodide gives rise to the aryl iodide (VII). This is converted into the arylboronic acid (VIII) by lithiation with butyllithium, followed by reaction with triisopropyl borate. Suzuki coupling between chloropyridine (IV) and boronic acid (VIII) leads to the phenylpyridine (IX). Reduction of the nitro group of (IX) employing sodium dithionite provides the diaminopyridine (X). This is finally condensed with triethyl orthopropionate to produce the target imidazopyridine compound.
4-Chloro-2-hydroxy-3-nitropyridine (I) is condensed with (S)-2-pentylamine (II) to produce the aminopyridine adduct (III). Subsequent chlorination of (III) by means of POCl3 furnishes the chloropyridine derivative (IV).