The cyclization of 2-bromo-4-isopropylphenylhydrazine (I) with 2-amino-2-propenenitrile (II) in refluxing 1N HCl gives 1-(2-bromo-4-isopropylphenyl)-3-methyl-1H-pyrrole-5-amine (III), which is acylated with propionic anhydride yielding the propionamide (IV). The reduction of (IV) with the complex borane/THF in THF affords the secondary amine (V), which is nitrosated with isoamyl nitrite in ethanol to give the nitroso compound (VI). The cyclization of (VI) in refluxing pyridine yields the imidazo[4,5-c]pyrrole (VII), which is finally alkylated with 2-bromopentane by means of sodium bis(trimethylsilyl)amide in hot DMF.