2,2-Diphenylethylamine (I) is converted into the corresponding formamide (II) upon refluxing in ethyl formate. Subsequent dehydration of formamide (II) with phosphorus oxychloride in the presence of diisopropylamine furnishes isocyanide (III)
The title compound is prepared according to the Ugi reaction by combination of the four components: isocyanide (III), m-cyanobenzaldehyde (IV), 2-benzoylbenzoic acid (V), and histamine (VI) in refluxing MeOH
Condensation of the pyridyl enaminone (I) with thiourea (II) in the presence of NaOEt gives 2-mercapto-4-(pyridin-2-yl)pyrimidine (III), which is alkylated with iodomethane, producing the corresponding methylsulfanyl pyrimidine (IV). Subsequent displacement of the methylsulfanyl group of (IV) with hydrazine leads to the hydrazino pyrimidine (V). Rhodium acetate-catalyzed coupling between 3-diazo-2,4-pentanedione (VI) and 4-chlorophenol (VII) furnishes the chlorophenyl ether (VIII). The tile pyrazole derivative is finally obtained by condensation between hydrazine (V) and diketone (VIII) in the presence of p-toluenesulfonic acid in boiling EtOH.