The Synthesis And Molecular Recognition Of Azacyclophanes

Due to their macrocyclic properties and structural versatility, cyclophanes take on potential application in the enzyme simulation, Host-Guest chemistry, self-assembly, selective catalysis and material science. The heterocyclophanes employing benzimidazlyl groups which have great biological activities can be used as biomolecular minics. By protonizing, quaternizing at the nitrogen atoms of benzimidazoles, or attaching active groups to the nitrogens, a lot of novle cyclophanes can be synthesized.In this paper, two series of benzimidazole cyclophanes were prepared from p-aminobenzoic acid and p-aminophenylacetic acid by acetylation, nitration, hydrolysis, nitro-reduction and cyclization. Factors influencing the product yields were discussed.An azo benzimidazole cyclophane was prepared from o-phenyldiamine and hexane diacid by condensation, nitration, bimolecular reduction. And also the azo benzimidazole cyclophane was obtained in another way by reduction of dinitrobisbenzimidazole to diaminobenzimidazole and diazotization.The aqueous solution of NaHSO₄/NaNO₃ provides a new reagent system for the chemselective nitration of aryl compounds, which improved the common technology using corrosive liquid nitric acid-sulfuric acid mixture as nitration reagent that seriously pollutes the environment and is very costly to treat. With this nitration method, the products were purified easily in high yields.To study the supramolecular systems of the host 1,6,20,25-tetraaza[6.1.6.1] paracyclophane CP₄₄ with three guests, 1-nitroso-2-naphthol, 2-nitroso-1-naphthol and cresol red, UV spectrometry titrimetric analysis was employed. When the concentrations of the guests were changed, the variation of the absorbanceΔA showed regular changes. It meaned that the host CP₄₄ formed 1:1 stoichiometric supramolecular complex with the guests.