1.2.5- Oxadiazole 2-oxides

N N 3-( p-Bromophenyl)-4-methyl- 1,2,5-oxadiazole 2-oxide 3-(p-bromo-phenyl)-4-methyl-l,2,5-oxadiazole 5-oxide 3,4-diphenyl-l,2,5-oxadiazole... 

Deviations of this magnitude are very unusual but can also be found for other sensitive heterocycles, such as 1,2,5-oxadiazole-2-oxides. Although the authors... 

Although benzofuroxan (Bfx) and furoxan (Fx) were first synthesized over 100 years ago, it was not until the middle of the 20th century that its relevant bioactivities were identified. Bfx s and Fx s relevant biological behaviors convert these systems in one of the most current study heterocycles in medicinal chemistry. Formally, these compounds are 1,2,5-oxadiazole hf-oxide derivatives, specifically Bfx should be named as benzo[l,2-c][l,2,5]oxadiazole 1-oxide and Fx as 1,2,5-oxadiazole 2-oxide, however, the common trivial... 

Thermal recyclization of the 3-diazenofuroxanyl unit to form the 4-nitro-l,2,3-triazole fragment has been found in noncondensed 1,2,5-oxadiazole 2-oxide derivatives (3,3 -azofuroxans) with acetamido substituents in the 4,4 -posi-tions <1999MC17>. 

The well-known method of furazan formation is based on nitrosation of alkenes. Thus, several NO donor 3,4-disubstituted 1,2,5-oxadiazole 2-oxide derivatives and the related 1,2,5-oxadiazoles, containing methylsulfonylphe-nyl, phenylsulfonyl, sulfonylamidophenyl, and phenylsulfonylamido groups were synthesized by nitration of... 

A novel approach to 1,2,4-thiadiazoles 112 is based on the monocyclic and cascade rearrangement of 1,2,5-oxadiazole-2-oxides 111 <2004PAC1691>. Thus, /V-oxidcs 110 upon treatment with ethoxycarbonyl isothiocyanate undergo cascade rearrangement to give 1,2,4-thiadiazoles 112 via intermediate 111 (Scheme 13). 

Di(2,3,4,6-tetra-0-acetyl-b-D-mannopyranosyl)-l,2,5-oxadiazole 2-oxide has been synthesized from D-mannose by a route, involving as the key step, dimerization of mannopyranosyl nitrile oxide. Three methods have been used for the generation of the nitrile oxide isocyanate-mediated dehydration of nitro-methylmannose derivative, treatment of aldoxime with aqueous hypochlorite and base-induced dehydrochlorination of hydroximoyl chloride. D-gluco, D-galacto, D-xylo and L-fucopyranosyl analogs has been prepared similarly. The structure of D-mannose-derived 1,2,5-oxadiazole 2-oxide has been established by X-ray crystallography (478). 

Furoxan is an old heterocyclic system, known to chemists thanks to an argument over its structure and its intriguing chemistry. NMR spectroscopy and X-ray crystallography resolved the problem of its structure and showed that it is the 1,2,5-oxadiazole 2-oxide (1). 

Furazane (1,2,5-Oxadiazole), Furazan-2-oxide (Furoxane, 1,2,5-Oxadiazol-2-oxide), Benzofurazane (2,1,3-Benzoxadiazole) und Benzofurazan-1 -oxide (Benzofuroxane,... 

Bei der Reduktion von -2-oxid mit Triethylphosphit (20° 48 h) werden lediglich 10% des Furazans isoliert. 

The energetics of the equilibrium between the isomeric thieno[2,3-c][l,2,5]oxadiazole A-mon-oxides (11) and (12) has been studied using low temperature NMR techniques, together with a comparison with other 1,2,5-oxadiazole 2-oxide systems <74JOC2956>. A similar study commented that the rate of isomerization between (13) and (14) is fast on the NMR timescale at room temperature. The equilibrium constant Kc for the isomerization between (13) and (14) is 65 whilst the free energy of activation for the isomerization is 51.3 kJ mol"1 <89JCS(P2)127>. 

Attempts to reduce furoxans (e.g., 3,4-dimethyl-1,2-5-oxadiazole 2-oxide) to anion-radicals led to paramagnetic products of indeterminate structure or multielectron reduction products. ... 

Compounds reported in the older literature as 1,2,3,6-dioxadiazines have now been assigned as 1,2,5-oxadiazole 2-oxides (furoxanes 1) (see Houben-Weyl, Vol. E8c, p450ff).4... 

Owing to their tendency to dimerize to furoxans (1,2,5-oxadiazole 2-oxides), nitrile oxides 5 are usually generated in situ, i.e., in the presence of suitable dipolarophiles such as alkenes, alkynes, etc., from stable precursors such as aldoximes 12 (X = H) or from primary nitroalkanes 13 (Scheme 2) [5,57-67]. Generation of nitrile oxides 5 from aldoximes 12 (X = H) involves either direct oxidation or halogenation of aldoximes 12 (X = H) to hydroximoyl halides 12 (X = Cl or Br) followed by dehydrohalogenation [5,57-67,79,80]. Alternatively, nitrile oxides 5 are conveniently generated via dehydration of primary nitroalkanes 13 [ 17,38,39,65,66,81-95]. This review covers the literature in the last 10-15 years pertaining to the chemistry of isoxazoHnes synthesized from primary nitroalkanes 13. 

Oxadiazole-2-oxides (furoxans) are generated by oxidative cychzation of the dioximes of 1,2-dicarbonyl compounds. As oxidants, NaOCl, Pb(OAc)4, or N2O4 have proved useful electrochemical oxidation is also possible [472]. 

C8H16N2O2S2, Dithiobismorpholine, 44B, 336 C9H5CINO, 3-Chloro-5-phenylisoxazole, 45B, 398 C9H6N2O2S, 7-Methylbenzothieno[3,2-c]furoxan, 41B, 422 C9H7BrN202, 4-Methyl-3-(p-bromophenyl)-1,2,5-oxadiazole 2-oxide,... 

I, 4-dinitro-2-methylpyrrole, ethylnitroHc acid and a derivative of furoxan (1,2,5-oxadiazole 2-oxide) 3-(5-methyl-4-furoxanyl)prop-2-enoic acid, which undergo decomposition to other products. Ascorbic acid completely eliminates the mutagenicity of 1,4-dinitro-2-methylpyrrole by reduction of the C-4 nitro group to a C-amino group. The l-nitro-2-methyl-4-amino pyrrole formed is non-mutagenic (Figure 11.1). 

---