Conjugated addition of 2-nitroaniline (I) to acrylonitrile (II) in the presence of Triton B in dioxane yielded propionitrile (III), which was hydrogenated to the phenylenediamine (IV). Treatment of ethyl cyanoacetate (V) with a cold saturated solution of HCl in absolute ethanol gave ethyl ethoxycarbonylacetimidate hydrochloride (VI). Reaction of this acetimidate (VI) with phenylenediamine (IV) in refluxing ethanol afforded the benzimidazole (VII), which was converted to the diester (VIII) on treatment with ethanolic HCl. Dieckmann condensation of diester (VIII) in the presence of sodium ethoxide furnished the tricyclic ketoester (IX), which was finally condensed with 2,6-difluoroaniline (X) in refluxing xilene to afford the target carboxamide.
Addition of acrylonitrile (II) to 3,4-difluoro-2-nitroaniline (I) gave the anilinopropionitrile (III). Subsequent hydrogenation of the nitro group of (III) over Pd/C led to the phenylenediamine (IV), which was condensed with carbethoxyacetimidate-HCl (V) to produce the benzimidazole (VI). After conversion of the nitrile group of (VI) to ester (VII) with ethanolic HCl, Dieckmann condensation using NaOEt furnished the cyclic ketoester (VIII). Finally, reaction of (VIII) with 2,6-difluoroaniline (IX) in xylene yielded the target carboxamide.