In a related procedure, amino isoxazole (IV) was converted to the corresponding isocyanate (VI) by treatment with phosgene and pyridine. Isocyanate (VI) was then condensed with amine (III), producing the target urea.
4-(4-Pyridinylmethyl)aniline (II) was prepared by catalytic hydrogenation of the corresponding nitro derivative (I) over Pd/C. Condensation of aniline (II) with N,N?carbonyldiimidazole produced the imidazolide (III). This was then condensed with 5-amino-3-tert-butyl-1-methylpyrazole (IV) to furnish the target urea.
Condensation of 4-aminophenol (I) with 4-chloropyridine (II) in the presence of potassium tert-butoxide afforded the intermediate diaryl ether (III).
Treatment of 3-amino-5-tert-butylisoxazole (IV) with carbonyldiimidazole produced the imidazolide (V), which was then condensed with amine (III) to furnish the title urea.
The cyclization of 2-pivaloylacetonitrile (I) with methylhydrazine (II) in refluxing ethanol gives 5-amino-3-tert-butyl-1-methylpyrazole (III), which is finally condensed with 4-(4-pyridylmethyl)aniline (IV) and carbonyldimidazole (CDI) in dichloromethane to afford the target urea. The aniline (IV) has been obtained by reduction of the corresponding nitro derivative (V) with H2 over Pd/C in ethanol.