Unexpected Heterocyclization of Electrophilic Alkenes by Tetranitromethane in the Presence of Triethylamine. Synthesis of 3-Nitroisoxazoles

The strategy for improving the stability of nitroform derivatives-high-energetic oxidant based on hexanitroethane

To develop high-energetic stability nitroform compounds, three types of nitroform derivatives based on hexanitroethane structure are designed. The guidelines for selecting these compounds are based on (1) constructing a flexible molecule and weakening the external force by elastic deformation and (2) forming negative ion or introducing electron-rich group to eliminate the electron-deficient situation. The conformations and some important properties of them are calculated at B3LYP/6-311 + G(d) level. Based on the bond order and bond dissociation enthalpy analysis, C-NO₂ bond is considered to be the most unstable position, and both of the methods can improve the stability of designed compounds. Based on molecular energy gap (HOMO-LUMO) and density of state (DOS) analysis, it is found that introducing of bridge atoms is helpful to lower the sensitivity, while the construction of anions changes both HOMO-LUMO and DOS which shows obvious ionic properties. A further study on the electrical potential surface shows that the probability for extreme values of designed compounds decreases which is beneficial for high stability. Finally, the explosive properties and impact sensitivity of them are calculated. Results show that their explosive performances are obviously better than current energetic oxidants and some of them maintain low sensitivity.

Regioselective synthesis of isoxazole and 1,2,4-oxadiazole-derived phosphonates via [3 + 2] cycloaddition

The regioselective synthesis of 3,4- and 3,5-disubstituted izoxazole- and 1,2,4-oxadiazole-derived phosphonates is described, including analogues of phosphohistidine.

Synthesis and biological evaluation of novel 5-hydroxylaminoisoxazole derivatives as lipoxygenase inhibitors and metabolism enhancing agents

A versatile synthesis of novel 5-hydroxylaminoisoxazoles bearing adamantane moieties has been accomplished using the heterocyclization reactions of readily available unsaturated esters by the treatment with tetranitromethane in the presence of triethylamine and subsequent reduction of resulting 5-nitroisoxazoles by SnCl2 with the participation of THF. A number of obtained isoxazole derivatives were evaluated for their antioxidative activity, inhibition of lipoxygenases and impact on the rat liver mitochondria. The majority of tested compounds demonstrated moderate antiradical activity in DPPH test (up to EC50 16μM). The same compounds strongly inhibited soybean lipoxygenase (up to IC50 0.4μM) and Fe(2+)- and Fe(3+)-induced lipid peroxidation (LP) of rat brain cortex homogenate (up to IC50 0.3μM). All tested isoxazole derivatives promoted the phosphorylating respiratory activity simultaneously with maximal stimulated respiratory activity of mitochondria and do not reveal any toxicity towards the primary culture of rat cortex neurons.

Convenient synthesis of energetic polynitro materials including (NO2)3CCH2CH2NH3-saltsviaMichael addition of trinitromethane

Acrylamide and nitroform are precursors for the formation of the 3,3,3-trinitropropylammonium cation, which was combined with several oxygen-containing anions in order to serve as potential HEDO salts.

Synthesis of 3,4,5-Trisubstituted Isoxazoles from Morita-Baylis-Hillman Acetates by an NaNO2 /I2 -Mediated Domino Reaction

An efficient NaNO2 /I2 -mediated one-pot transformation of Morita-Baylis-Hillman (MBH) acetates into alkyl 3-nitro-5-(aryl/alkyl)isoxazole-4-carboxylates is described. In a cascade event, initial Michael addition of NaNO2 to the MBH acetate furnishes the allylnitro intermediate which undergoes I2 -catalyzed oxidative α-CH nitration of the nitromethyl subunit followed by [3+2] cycloaddition to afford the title compounds. Structural elaborations of these highly substituted isoxazoles by SN Ar reactions and hydrogenolysis allows access to useful products.

NIS-mediated oxidative cyclization of N-(2-trifluoromethyl-3-alkynyl) hydroxylamines: a facile access to 4-trifluoromethyl-5-acylisoxazoles

A NIS mediated sequential procedure involving oxidation and electrophilic cycloisomerization ofN-(2-trifluoromethyl-3-alkynyl) hydroxylamines for 4-trifluoromethyl-5-acylisoxazole synthesis is developed.