Phenyl pyrrole (III) was prepared by Clauson-Kaas reaction of 4-methoxy-2-nitroaniline (I) with 2,5-dimethoxytetrahydrofuran (II). Subsequent reduction of the nitro group of (III) using hydrazine and Raney Nickel provided aniline (IV), which was cyclized with phosgene in refluxing toluene to furnish the pyrroloquinoxaline (V). This was chlorinated with POCl3 to obtain the chloroquinoxaline (VI). Finally, nucleophilic substitution in (VI) with N-(4-fluorobenzyl)piperazine (VII) yielded the title compound.
A synthesis for the 18F-labeled compound has also been reported. The piperazinylquinoxaline (IX) was obtained from chloroquinoxaline (VI) and excess piperazine (VIII) at 160 C. This was then alkylated with 4-[18F]fluorobenzyl iodide (X) in refluxing CH2Cl2 to provide the labeled product.