A facile access to novel spiroxindole fused pyrrolidine and thiazolo pyrrolidine benzimidazole derivatives via 1,3-dipolar cycloaddition reaction

R1 = H, 5-bromo, chloro; R2 = H, methyl, ethyl, allyl; R3 = 4-chloro, bromo, fluoro, methyl, methoxy and 2-chloro, bromo.