<i>ortho</i>-Functionalized nitroarenes in the synthesis of heterocycles

The development of convenient methods for the synthesis of heterocyclic compounds that are highly important for the search of pharmacological substances and in other spheres of human activity is among the most relevant fields of organic chemistry. Two functional groups in arenes located in adjacent positions of the benzene ring can provide a fused ring. If at least one of the two <i>ortho</i>-functional groups contains a nitrogen atom, a nitrogen heterocycle is formed upon the cyclization. The nitro group is often chosen as the nitrogen-containing group in <i>ortho</i>-substituted arenes to form heterocyclic systems, because of ready availability of <i>ortho</i>-functionalized nitroarenes, the ability of nitro group to undergo various reactions and selectivity of the reactions. This review integrates and analyzes for the first time published data on the involvement of <i>ortho</i>-functionalized nitroarenes in the design of heterocyclic structures. Using numerous examples reported in the literature in the last decade, the mutually beneficial effect of two <i>ortho</i>-functional groups, one of which is the nitro group, for the formation of various heterocycles is demonstrated. Examples of both intramolecular cyclizations and reactions involving additional reagents are considered. The review gives a holistic view of the potential of functionalized <i>ortho</i>-nitroarenes in the design of various heterocyclic systems. <br> The bibliography includes 132 references.