Novel synthesis of biologically active nitro heterocyclic compounds

Introduction A vast number of heterocyclic moieties are used in pharmaceutical research, agricultural science and drug discovery. Heterocyclic building blocks also have practical use as components in dyestuffs, antioxidants, copolymers, bases and ligands. Nitro heterocyclic compounds have diverse biological activity, antiinflammatory or vasodilator activity and structure activity relationship, and have been commonly used in sedatives, hypnotics, narcotics, etc. Nitro imidazole had been used against amoebic, trichomal, giradial and anaerobic bacterial infections as antabuse agents. Imidazole derivatives bearing both phenyl and nitro groups show antiprotozoic activity. Benzimidazole compounds control a large number of fungal diseases. Similarly, 2, 5-disubstituted pyridine is reported in many biologically active compounds. Conventional nitration methods involve use of nitrating mixture, nitronium tetrafluroborate / acetonitrile, nitric acid/acetic anhydride, etc., require a lot of time, toxic and corrosive chemicals, and are associated with disposal problems of waste and by products, and presents a serious environmental concern. This study presents new environment friendly nitration method involving the use of bismuth nitrate supported on silica gel as a solid support for synthesis of nitro heterocyclic compounds. Experimental Procedure All chemicals were of LR grade (S. d. Fine Chem. Ltd.). The completion of reaction and purity of products were checked by silica gel TLC. Melting points were determined by open capillary method. IR spectra were recorded (KBr pellets) on Shimadzu FTIR-8400 Spectrophotometer. H NMR spectra were recorded on Varian Mercury spectrometer at 300 MHz in CDCl 3 using TMS as internal standard. A Kenstar (OM 99181 C, 2350 W) monomode microwave oven with facility to change the power level used to carry out the reactions.