Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• chlorides to form furoxans also known as 1,2,5-oxadiazole 2-oxides, a class of structures with important biological activities due to their unique electronic nature and coordination ability. Keywords: environmentally friendly; furoxans; 1,2,5-oxadiazole 2-oxides; trifluoromethyl-substituted isoxazoles

• with 95% yield (5% water, 95% methanol, room temperature, 2 hours; see Table 1, entry 15), which adds another method for the synthesis of furoxans to the current literature. The synthesis of furoxans or 1,2,5-oxadiazole-2-oxides was first reported by Kekulé in 1857 [36]. Since then, these nitric oxide

• donors have shown important biological activities due to their unique electronic and coordination ability [37][38], such as antitumor [39] and antiparasitic [40][41]. Previously, furoxans were synthesized via dimerization of hydroximoyl chlorides in the presence of a base, such as trimethylamine in ether

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• dipoles not only react with various dipolarophiles but also undergo spontaneous dimerization to form furoxans. To avoid or minimize this drawback, the substitutents (e.g., Cl or Me) around the CNO group were introduced to stabilize the nitrile oxides even at room temperature [46][47]. Here, the 2,6

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• the design of pharmacology-oriented heterocyclic systems. Keywords: CH acids; dearomatization; 1,4-dihydropyridines; furoxans; nitropyridines; Introduction The reactions of condensed furoxans with CH acidic compounds have been extensively studied. There are two main possibilities for these reactions

• , 1,3-dicarbonyl compounds, etc. on furoxans annelated with benzene or heterocyclic ring in the presence of base (Scheme 1). Mononitrobenzofuroxans as well as pyridofuroxan (4-azabenzofuroxan) react as mentioned above [11][12][13][14]. At the same time in the case of highly electrophilic 4,6

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime

• Raoni S. B. Gonçalves,
• Michael Dos Santos,
• Guillaume Bernadat,
• Danièle Bonnet-Delpon and
• Benoit Crousse

Beilstein J. Org. Chem. 2013, 9, 2387–2394, doi:10.3762/bjoc.9.275

• revealed the presence of a side product and despite the total consumption of the aldoxime, a small amount of allylbenzene remained. It is known that nitrile oxides can dimerize or isomerize to yield different products, such as furoxans, isocyanates, 1,2,4-oxadiazoles and 1,4,2,5-dioxadiazines (Figure 2

A surprising new route to 4-nitro-3-phenylisoxazole

• Henning Hopf,
• Aboul-fetouh E. Mourad and
• Peter G. Jones

Beilstein J. Org. Chem. 2010, 6, No. 68, doi:10.3762/bjoc.6.68

• and smetic mesophases associated with their rod-like core structure [9]. The pioneering work on furoxans as nitric oxide donors by Gasco et al. has stimulated a large number of further studies. One of these reports deals with a synthetic route and structural characterization of two isomeric