Nitrone reactions nitration

Nitrones, reaction with olefins, 46, 130 Nitronium tetrafluoroborate, from nitric add, boron trifluoride, and hydrogen fluoride, 47, 56 in nitration of aromatic rings, 47, 60... 

Nitronate(47a) is not the only oxazete derivative. For example, sterically hindered nitroalkenes (42b-d) can be prepared by nitration and halogenation of readily available allenes (48). Compounds (42b-d) are rather smoothly isomerized into the corresponding four-membered cyclic nitronates (47b-d) by the first-order reaction equation (168). Storage of nitronate (47c) is accompanied by its slow transformation into acid chloride (47e) from which amide (47f) can be easily synthesized. 

A few nucleophiles either did not give any spin adduct with PBN or directly gave the benzoyl nitrone [9], Bromide ion did not give any spin adduct, explicable by the very short lifetime of Br-PBN (Rehorek and Janzen, 1984) and trifluoroacetate, nitrate, phenylsulfinate and chloride ion produced [9]. This can either be explained by the rapid further oxidation of the spin adduct formed [similar to reaction (29) see Table 4] or a rapid solvolysis reaction of the latter (Scheme 2), forming [9] by reaction of the intermediate carbocation... 

Decarboxylation of 1,3-dimethylorotic acid in the presence of benzyl bromide yields 6-benzyl-1,3-dimethyluracil and presumably involves a C(6) centered nucleophilic intermediate which could nonetheless have either a carbene or ylide structure. Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry has been used to explore the gas-phase reactions of methyl nitrate with anions from active methylene compounds anions of aliphatic ketones and nitriles react by the 5n2 mechanism and Fco reactions yielding N02 ions are also observed nitronate ions are formed on reaction with the carbanions derived from toluenes and methylpyridines. 

Nitronate salts can react with alkyl halides to yield polynitroaliphatic compounds with varying degrees of success. The main by-products of these reactions arise for competitive 0-alkylation. Alkyl nitrates are formed as by-products when the nitroform anion is used in these reactions. ... 

Oxidative nitration, a process discovered by Kaplan and Shechter, is probably the most efficient and useful method available for the synthesis of em-dinitroaliphatic compounds from the corresponding nitroalkanes. The process, which is an electron-transfer substitution at saturated carbon, involves treatment of the nitronate salts of primary or secondary nitroalkanes with silver nitrate and an inorganic nitrite in neutral or alkali media. The reaction is believed ° °° to proceed through the addition complex (82) which collapses and leads to oxidative addition of nitrite anion to the nitronate and reduction of silver from Ag+ to Ag . Reactions proceed rapidly in homogeneous solution between 0 and 30 °C. 

A major drawback of the Kaplan-Shechter reaction is the use of expensive silver nitrate as one of the reagents, which prevents scale up to an industrial capacity. Urbanski and co-workers modified the process by showing that the silver nitrate component can be replaced with an inorganic one-electron transfer agent like ferricyanide anion. In a standard procedure the nitroalkane or the corresponding nitronate salt is treated in alkaline media with potassium... 

Feuer and co-workers extended their studies to the alkaline nitration of a,Nitration with potassium ferf-butoxide and amyl nitrate in THF at —30 °C yields the corresponding dipotassium salt of the a,nitronate salts from these reactions are isolated via methanol-induced precipitation from the aqueous reaction liquors, a process which also separates the product from impurities. These salts undergo hydrolysis on treatment with aqueous potassium hydroxide, and subsequent acidification yields the corresponding Q, y-dinitroalkane. This route has been used to synthesize 1,4-dinitrobutane (27) from apidonitrile (95) in 30 % overall yield. 

Mannich bases derived from polynitroalkanes are usually unstable because of the facile reverse reaction leading to stabilized nitronate anions. The nitration of Mannich bases to nitramines enhances their stability by reducing the electron density on the amine nitrogen through delocalization with the nitro group. The nitration of Mannich bases has been exploited for the synthesis of numerous explosives, some containing both C-NO2 and N-NO2 functionality. Three such compounds, (163), (164) and (165), are illustrated below and others are discussed in Section 6.10. 

Paquette and co-workers synthesized the 5,11-dinitro isomer of 1,3-bishomopentaprismane (95) by treating the dioxime (94) with a buffered solution of m-CPBA in refluxing acetonitrile. A significant amount of lactone by-product (96) is formed during this step and may account for the low isolated yield of (95). Oxidative nitration of (95) with sodium nitrite and potassium ferricyanide in alkaline solution yields a mixture of isomeric trinitro derivatives, (97) and (98), in addition to the expected 5,5,11,11-tetranitro derivative (99), albeit in low yield. Incomplete reactant to product conversion in this reaction may result from the low solubility of either (97) or (98) in the reaction medium, and hence, incomplete formation of the intermediate nitronate anions. 

The other products of the equivalents of K S, HS are nitrate of potassa—KO, NOs—and a little ammonia. No trace of nitrate could be discovered in the solution, which was evaporated to dryness with excess of acetic acid, to expel the nitrons acid. An attempt was made to turn the reaction of KS, HS upon gun-cotton to account in effecting the determination of the nitrogen by this means but the results were unsatisfactory, in consequence of the co-existence of ammonia and nitrous acid in the liquid, The solution could not bo heated to expel the former without risk of loss in the weight of the roducad cotton, neither could the ammonia be retained by addition of an acid, without escape of NO,-from the action of sulphide of hydrogen and nitrous acid on each other. 

Reaction of alkyl halides with sodium nitrite Nitromercuration of alkcncs Formation of nitroalkancs from nitrate esters Chemical properties of nitroalkancs Nitronic acids... 

Potassium perchlorate may be detected in mixtures by the methylene blue reaction (see under Potassium Chlorate). It may be estimated quantitatively by heating, as described under Potassium Nitrate, or by nitron also by precipitation as methylene blue perchlorate and titration of the excess of methylene blue with picric acid. It can also be reduced with titanous sulphate or chloride. 

The isoxazoline is also obtained from other reactions with pyridinium nitrate and pyrrolidine <89JHC1569>. Silyl nitronate (259) (R = H, Me, Et, Ph) with Ar-acrylyl-(2/ )-bornane-10,2-sultam (260) yielded a mixture of adducts. Further treatment with p-toluene sulfonic acid afforded the diastereomeric isoxazoline (261) (Equation (45)) <91PHC166>. 

Nitration. The synthesis of gem-dinitroalkanes by reaction of nitronate anions with the combined salts is efficient. 

Triazoles are important as reagents. 1,2,4-Triazole is useful as a catalyst for transacylation reactions, e.g. for the synthesis of peptides from A -protected amino-4-nitrophenyl esters and amino acids without racemization. Nitron 5, a mesoionic 1,2,4-triazole, forms an almost insoluble nitrate and is used for the detection and gravimetric determination of nitrate ions. Nitron forms a covalent compound with poly(4-chloromethylstyrene) which removes nitrate from drinking water. 

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