Five-Membered Hetarene N-Oxides: Recent Advances in Synthesis and Reactivity

Abstract

Five-membered heterocyclic N-oxides attracted special attention due to their strong application potential in medicinal chemistry and advanced materials science. In this regard, novel methods for their synthesis and functionalization are constantly required. In this short review, recent state-of-the-art achievements in the chemistry of isoxazoline N-oxides, 1,2,3-triazole 1-oxides and 1,2,5-oxadiazole 2-oxides are briefly summarized. Main routes to transition-metal-catalyzed and metal-free functionalization protocols along with mechanistic considerations are outlined. Transformation patterns of the hetarene N-oxide rings as precursors to other nitrogen heterocyclic systems are also presented.

NOBF4-Mediated Assembly of the Sydnone Imine Scaffold in the Synthesis of Double Nitric Oxide Donors

“…Methods for the construction and functionalization of the furoxan ring along with an incorporation of the furoxan scaffold into the structure of various drug candidates to improve their pharmacokinetic profiles have been widely explored in recent years. 8` b c d On the contrary, assembly of the sydnone imine moiety is based on a single existing procedure comprising of a nitrosation of α-amino nitrile derivatives with NaNO 2 in aqueous acid solutions or alkyl nitrites followed by acid-promoted cyclization (Scheme 1 A). 17 However, this approach is not applicable for α-amino nitriles bearing an electron-withdrawing substituent due to the low nucleophilicity of the NH-fragment.…”

Preparation of Ring-Methoxylated Arylnitromethanes by the Victor Meyer Reaction

“…Arylnitromethanes (ANMs) are valuable synthetic intermediates that have been used for the synthesis of a variety of aryl aliphatic compounds and different types of heterocycles bearing aryl groups. 1 2 3 4 5 In our previous work, nitrostilbenes prepared from ANMs were utilized as starting materials for the synthesis of 3,4-diaryl-pyrroles and -isoxazoles. 6,7…”

“…Arylnitromethanes (ANMs) are valuable synthetic intermediates that have been used for the synthesis of a variety of aryl aliphatic compounds and different types of heterocycles bearing aryl groups. [1][2][3][4][5] In our previous work, nitrostilbenes prepared from ANMs were utilized as starting materials for the synthesis of 3,4-diaryl-pyrroles and -isoxazoles. 6,7 The Victor Meyer reaction, [8][9][10][11][12][13][14][15][16][17][18][19] which involves the reaction of an alkyl halide with silver nitrite in a nonpolar solvent, e.g., diethyl ether or benzene, has been the method of choice for the preparation of ANMs since the 19th century.…”

Recent progress in synthesis and application of furoxan

“…22 This review paper discusses the recent developments in the synthesis of furoxans based on the PRIS strategy, classifying them according to the type of substituents to be introduced. Several new methods of substituent modication other than PRIS have also been developed in recent years, 23 but are not included in this review. In addition to synthesis, several topics of applied research on furoxan molecules, most of which have been made possible based on the recent synthetic developments, will also be presented.…”