In the present reaction series, a convenient method for the synthesis of 1-N-ethoxyphthalimido-2-[(1,3-dioxo-1,3- dihydro-2H-isoindolyl)alkyl]benz-imidazole (3.1-IVa-c) is described. Phthalic anhydride was made to react with ω-amino acids (glycine/alanine/phenylalanine) (3.1-Ia-c) in dry condition without using any solvent, to yield 1,3-dioxo-1,3-dihydro-2H- isoindole-2-yl)acetic/propanoic/2-phenyl acetic acid (3.1-IIa-c). The chemoselective reaction of –COOH group present in (3.1-IIa-
c) with o-phenylenediamine led to the formation of 2-[1-(1H- benzimidazole-1-yl)methyl]-1H-isoindole-1,3(2H)-dione (3.1- IIIa), 2-[1-(1H-benzimidazole-2-yl)ethyl]-1H-isoindole-1,3(2H)- dione (3.1-IIIb) and 2-[1-(1H-benzimidazole-1-yl)benzyl]-1H- isoindole-1,3(2H)-dione (3.1-IIIc) respectively. Replacement of imidazole NH proton of (3.1-IIIa-c) from ethoxyphthalimide moiety was carried out by their condensation with phthalimidoxyethyl bromide (2.I-II), resulted in the final compound (3.I-IVa-c). All the compounds were characterized by elemental analysis, IR, NMR and mass spectroscopy .