The reaction of 2-chlorobenzimidazole (I) with 2-chloroethyl ethyl ether (II) by means of NaOH in DMF gives 1-(2-ethoxyethyl)benzimidazole (III), which is then condensed with N-methylhomopiperazine (IV) at 120 C.
A new synthesis of KB-2413 has been described: The reaction of 2-chloronitrobenzene (I) with 2-ethoxyethylamine (II) gives 1-(2-ethoxyethylamino)-2-nitrobenzene (III), which is reduced with Zn and NaOH to N-(2-ethoxyethyl-o-phenylenediamine (IV). The cyclization of (IV) with urea in amyl alcohol affords 1-(2-ethoxyethyl)benzimidazol-2-one (V), which is treated with refluxing POCl3 yielding 2-chloro-1-(2-ethoxyethyl)benzimidazole (VI). Finally, this compound is condensed with N-methylhexahydro-1,4-diazepine (VII) and treated with fumaric acid.