Direct Synthesis of N-(1,2,5-Oxadiazolyl)hydrazones through a Diazotization/Reduction/Condensation Cascade

4-Amino-3-(1-{[amino(3-methyl-2-oxido-1,2,5-oxadiazol-4-yl)methylene]hydrazinylidene}ethyl)-1,2,5-oxadiazole 2-Oxide

Functionally substituted 1,2,5-oxadiazole 2-oxides (furoxans) are important pharmaceutical scaffolds used for the preparation of various pharmacologically active substances. Furoxans bearing hydrazone functionality are considered as promising drug candidates for the treatment of neglected diseases. However, pharmacologically oriented hydrazones derived from (furoxanyl)amidrazones and acetylfuroxans have remained unknown so far. In this communication, a simple method for the synthesis of 4-amino-3-(1-{[amino(3-methyl-2-oxido-1,2,5-oxadiazol-4-yl)methylene]hydrazinylidene}ethyl)-1,2,5-oxadiazole 2-oxide is described. The structure of the synthesized compound was established by elemental analysis, high-resolution mass spectrometry, 1H, 13C NMR and IR spectroscopy.

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

Five-membered heterocyclic N-oxides attract special attention due to their significant potential applications in medicinal chemistry and advanced materials science. In this regard, novel methods for their synthesis and functionalization are in constant demand. 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 summarized. The main routes involving transition-metal-catalyzed and metal-free functionalization protocols along with mechanistic considerations are outlined. The transformations of these hetarene N-oxide rings as precursors to other nitrogen heterocyclic systems are also presented.

1 Introduction

2 Isoxazoline N-Oxides

3 1,2,3-Triazole 1-Oxides

4 1,2,5-Oxadiazole 2-Oxides

5 Conclusion

Recent Advances in the Synthesis and Biomedical Applications of Heterocyclic NO-Donors

Nitric oxide (NO) is a key signaling molecule that acts in various physiological processes such as cellular metabolism, vasodilation and transmission of nerve impulses. A wide number of vascular diseases as well as various immune and neurodegenerative disorders were found to be directly associated with a disruption of NO production in living organisms. These issues justify a constant search of novel NO-donors with improved pharmacokinetic profiles and prolonged action. In a series of known structural classes capable of NO release, heterocyclic NO-donors are of special importance due to their increased hydrolytic stability and low toxicity. It is no wonder that synthetic and biochemical investigations of heterocyclic NO-donors have emerged significantly in recent years. In this review, we summarized recent advances in the synthesis, reactivity and biomedical applications of promising heterocyclic NO-donors (furoxans, sydnone imines, pyridazine dioxides, azasydnones). The synthetic potential of each heterocyclic system along with biochemical mechanisms of action are emphasized.