Quinoline N‐Oxide: A Versatile Precursor in Organic Transformations

Quinoline derivatives are very widely known biologically active heterocyclic compounds, as for example quinine, mefloquine, etc. In recent years, the interests of researchers are growing to look for a methodology using quinoline N-oxides as a precursor to make several bio-active quinoline compounds as quinoline N-oxides are more reactive with good regioselectivity than unoxidized quinolines. In this review, numerous procedures are discussed using quinoline N-oxides as a versatile precursor in organic transformations, such as alkenylation, alkylation, arylation, amination, amidation, halogenation and so on under metal or metal-free conditions at C-2, C-3 or C-8 positions. The main focus of this context is to explore various procedures of synthesis of quinoline derivatives with good regioselectivity, to understand the extent of usefulness of those procedures through the study of scope of substrates and the reaction mechanisms of the processes.