Quinoline N‐Oxide: A Versatile Precursor in Organic Transformations

Abstract

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.

Peroxodicarbonate – a renaissance of an electrochemically generated green oxidizer

“…N-Oxides also represent an important structure in organic chemistry like precursors to several rearrangements as well as metabolites in organisms. [71][72][73][74][75][76][77][78][79][80][81][82] Gooßen and co-workers established the N-oxidation of tertiary amines using a 0.25 M 1 solution. It was found that addition of 0.25 eq.…”

Selective Deuteration of Heterocycle N-Oxides via Iridium-Catalysed Hydrogen Isotope Exchange

“…Based on this, we were motivated to explore other polycyclic aromatic systems where labelling might be directed, in a complementary manner, into the ring adjacent to that bearing the directing group. To this end, we selected the quinoline N -oxide 8 motif for our initial study in this area, based on the ubiquity of quinolines within pharmaceuticals and bioactive natural products. 9 Encouragingly, there are a number of reports on the C–H activation of this system, 10 resulting in selective functionalisation at C8.…”

Three-Step Synthesis of N-(7-chloro-4-morpholinoquinolin-2-yl)benzamide from 4,7-Dichloroquinoline

“…Due to the paramount significance of the functionalized quinoline core in the search for drug candidates and medicinal chemistry, the development of new synthetic methodologies remains an active area. Among modern methodologies, there is regioselective functionalization of the quinoline ring through C-H activation, especially via N-oxide formation, using it as a directing group [21,22]. The latter is considered one of the most powerful and, thus, attractive approaches for synthesizing C-2 and C-8 functionalized quinoline compounds under mild reaction conditions [23][24][25][26].…”