Condensation between ethyl 2-oxocyclopentanecarboxylate (I) and thiourea (II) gives rise to the thiouracil derivative (III) (1,2). This is then alkylated with 4-fluorobenzyl chloride (IV) to yield thioether (V). Subsequent alkylation of (V) with tert-butyl iodoacetate (VI) furnishes adduct (VII). Further acidic cleavage of the tert-butyl ester group of (VII) leads to carboxylic acid (VIII) (2,3). Alternatively, intermediate (VIII) is prepared by alkylation of (V) with triflate (IX), followed by alkaline hydrolysis of the resultant methyl ester (X)
Suzuki coupling between 4-bromobenzaldehyde (XI) and 4-trifluoromethylbenzeneboronic acid (XII) affords the biphenylyl aldehyde (XIII). This is then reductively aminated with N,N-diethylethylenediamine (XIV) and NaBH4 to produce diamine (XV) (1,3). Finally, coupling between amine (XV) and carboxylic acid (VIII) leads to the title carboxamide