Recent Advances in Cycloaddition Reactions of Heterocyclic N-Oxides

Abstract

1,3-Dipolar cycloaddition of N-oxides of azines and azoles has become a reliable and versatile synthetic method of preparation of highly functionalized nitrogen heterocycles. Mechanisms of cycloaddition of N-oxides are outlined, including various reaction pathways available for the initial five-membered cycloadducts. Cycloaddition to multiple carbon-carbon, carbon-nitrogen, and carbon-sulfur bonds is discussed, with particular emphasis on modern methods of selective C-2-functionalization of the heteroaromatic ring.

Complexes of 1,10-Phenanthroline-Mono-N-Oxides with Copper(Ii) and Nickel(Ii) in Aqueous Solution and Solid Phase

“…These compounds are the subject of interest due to their widespread possible applications in organic chemistry (phase transfer catalysis, cycloaddition reactions, organocatalysis, etc.). [2][3][4] Earlier studies implied that the oxidation of phen-s is not a trivial task and vigorous experimental procedures are required to yield the corresponding phenO-s. Recently, we have confirmed that phen-s can readily be oxidized to N-oxides by Oxone (KHSO 5 ) under relatively mild conditions in aqueous solution and we have developed a method to synthesize a series of 1,10-phenanthroline-N-oxides.…”

Recent Advances in the Synthesis of C2‐Functionalized Pyridines and Quinolines Using N‐Oxide Chemistry

“…[7] Loska reviewed pyridine N-oxide cycloadditions in 2015 [8] and 2017. [9] Quinoline N-oxide alkenylations were reviewed by Kouznetsov and coworkers in 2020. [10]…”

Synthesis and Characterization of 1,10-Phenanthroline-mono-N-oxides

“…N-oxides of heterocycles are of great importance due to their widespread applicability, including, but not limited to, manufacturing chirality chemosensors [1], oxidizing agents in annulation reactions [2], intramolecular oxidants in Baeyer-Villiger reaction of ketones [3], directing group and source of oxygen atom in sulfonylation reactions [4], phase-transfer catalysts in enantioselective transformations [5], starting materials in C-C bond forming processes [6][7][8][9], or in the synthesis of 2-aminopyridines [10] and N-azine sulfoximines [11]. Recently published papers have discussed the cycloaddition reactions of N-oxides [12], their photochemistry [13,14] and their applications in organocatalysis [15][16][17]. Within this family of compounds, only limited information is available on 1,10-phenanthroline-1-Noxide (phenO) and its derivatives.…”