1) The reaction of 1-(4-nitrophenyl)piperazine (I) with tert-butyl dicarbonate (II) and triethylamine in dichloromethane gives 4-(4-nitrophenyl)piperazine-1-carboxylic acid tert-butyl ester (III), which is reduced with H2 over Pd/C, yielding the corresponding 4-amino compound (IV). The reaction of (IV) with phenyl chloroformate (V) and triethylamine in dichloromethane affords the carbamate (VI), which by reaction with hydrazine is converted into the semicarbazide (VII). The cyclization of (VII) with formamidine (VIII) and triethylamine in hot 2-methoxyethanol affords the triazolone (IX), which is condensed with 4-(trifluoromethoxy)benzyl bromide (X) by means of Cs2CO3 in DMF, giving the disubstituted triazolone (XI). The deprotection, elimination of the tert-butoxycarbonyl group, of (XI) with HCl yields the monosubstituted piperazine (XII), which is finally condensed with (2R,3S)-oxirane (XIII) by means of LiClO4 in refluxing acetonitrile.
2) The addition of 1-(4-nitrophenyl)piperazine (I) to the chiral oxirane (XIII) as before gives the disubstituted piperazine (XIV), which is hydrogenated with H2 over Pd/C in ethyl acetate, yielding the anilino derivative (XV). The acylation of (XV) with phenyl chloroformate (V) and triethylamine in dichloromethane affords the carbamate (XVI), which is treated with hydrazine to give the semicarbazide (XVII). The cyclization of (XVII) with formamidine (VIII) as before affords the triazolone (XVIII), which is finally condensed with 4-(trifluoromethoxy)benzyl bromide (X) by means of Cs2CO3 in DMF.