Affiliation: Department of Chemistry, Semnan University, P.O. Box 35195-363 Semnan, Iran and Faculty of Chemistry, Bu-Ali Sina University, Hamedan P.O. Box 6517838683, Iran.
It is difficult to imagine organic chemistry without organo-halogen compounds and the molecular halogens needed for their preparation. In fact, It is implied that halogenation of organic compounds is a key industrial process; for example, the halogenated products are used in the synthesis of many pesticides and pharmaceuticals. Conventional halogenation methods typically use pollutant, toxic and corrosive elemental halogens (X2), which also generate hydrohalic acid as byproduct and effectively reduce the atom efficiency. Hence, to avoid their use, various modified reagents (N-halo reagents such as trichloisocyanuric acid, haloglycolurils, N-halosuccinimid and …), methods such as oxidative halogenation in the presence of alkali halogen salts, biohalogenations, solid phase and ionic liquid have been developed. In this review article, we will focus on strategies that are much greener and more sustainable than those using elemental halogens.