The esterification of vanillic acid (I) with benzyl bromide and K2CO3 in DMF gives the protected benzyl ester (II), which is nitrated with conc. HNO3 in acetic acid to yield 4-benzyloxy-5-methoxy-2-nitrobenzoic acid benzyl ester (III). The reduction of (III) with SnCl2 in ethyl acetate affords the corresponding 2-amino compound (IV), which is cyclized with ammonium formate in DMF at 150 C to provide the quinazolinone (V). The reaction of (V) with refluxing SOCl2 gives the chloro derivative (VI), which is condensed with 1-(tert-butoxycarbonyl)piperazine (VII) by means of DIEA in hot THF to give the 4-piperazinyl quinazoline (VIII). The reductive cleavage of the benzyl protecting group of (VIII) by means of H2 over Pd/C in ethanol yields the hydroxy compound (IX), which is condensed with 3-(tosyloxy)propyl chloride (X) by means of Cs2CO3 in DMF to afford the corresponding ether (XI). The reaction of the tosyloxy group of (XI) with piperidine (XII) in DMF provides the piperidinyl derivative (XIII), which is Boc deprotected by treatment with HCl in dioxane to give the piperazinyl precursor (XIV). Finally, this compound is condensed with 4-isopropoxyphenyl isocyanate (XV) in DMF to yield the target piperazine carboxamide.

The esterification of vanillic acid (I) with benzyl bromide and K2CO3 in DMF gives the protected benzyl ester (II), which is nitrated with conc. HNO3 in acetic acid to yield 4-benzyloxy-5-methoxy-2-nitrobenzoic acid benzyl ester (III). The reduction of (III) with SnCl2 in ethyl acetate affords the corresponding 2-amino compound (IV), which is cyclized with ammonium formate in DMF at 150 C to provide the quinazolinone (V). The reaction of (V) with refluxing SOCl2 gives the chloro derivative (VI), which is condensed with 1-(tert-butoxycarbonyl)piperazine (VII) by means of DIEA in hot THF to give the 4-piperazinyl quinazoline (VIII). The reductive cleavage of the benzyl protecting group of (VIII) by means of H2 over P/C in ethanol yields the hydroxy compound (IX), which is condensed with 3-(tosyloxy)propyl chloride (X) by means of Cs2CO3 in DMF to afford the corresponding ether (XI). The reaction of the tosyloxy group of (XI) with morpholine (XII) in DMF provides the morpholinyl derivative (XIII), which is Boc deprotected by treatment with HCl in dioxane to give the piperazinyl precursor (XIV). Finally, this compound is condensed with 4-isopropoxyphenyl isocyanate (XV) in DMF to yield the target piperazine carboxamide.