"In water" syntheses of heterocyclic compounds

Recently an aqueous medium has attracted the interest of chemists for many organic synthesis, and sometimes, surprising discoveries have been made using water. Among the various organic reactions investigated in aqueous medium, the synthesis of heterocyclic compounds has been the most widely studied because heterocyclic compounds are rich sources of diverse physical, chemical, and biological properties. They are commonly used as templates to design biologically active agents in medicinal chemistry. Moreover, in the past 20 years, the drug-discovery process has undergone extraordinary changes, and high-throughput biological screening of potential drug candidates has led to an ever-increasing demand for novel drug, based on heterocyclic compounds. Noteworthy advantages were observed during the course of our study on "in water" synthesis of heterocyclic compounds. The established advantages of water as a solvent for reactions are: water is the most abundant and available resource on the planet and many biochemical processes occur in aqueous medium. This review is focussed on the use of water in the synthesis of heterocycles. Heterocycles that will be covered include acridine, benzothiazole, benzopyran, isoxazole, pyradazine, pyrazole, pyridine, pyrimidine, pyrrole, quinazoline, quinoline, quinoxaline, thiadiazole, triazole, xanthene, xanthone and others.