Nitrosonium tetrafluoroborate

Nitration has also been effected with the complexes from dinitrogen tetroxide and Lewis acidsin the case of boron trifluoride the complex appears to be a mixture of nitronium and nitrosonium tetrafluoroborates. ... 

Equations 1-10 illustrate some mild methods that can be used to cleave amides. Equations 1 and 2 indicate the conditions that were used by Woodward and Eschenmoser, respectively, in their synthesis of vitamin B12. Butyl nitrite, nitrosyl chloride, and nitrosonium tetrafluoroborate (NO BF4 ) have also been used to cleave amides. Since only tertiary amides are cleaved by potassium -butoxide (eq. 3), this method can be used to effect selective cleavage of tertiary amides in the presence of primary or secondary amides.(Esters, however, are cleaved by similar conditions.) Photolytic cleavage of nitro amides (eq. 4) is discussed in a review. 

Nitrosonium tetrafluoroborate has been proposed as an alternative to NaN02/HBF4. 2-Fluoropyridine is obtained in 69% yield on warming a CH2C12 mixture of NOBF4 with 2-NHrpyridine (90EUP430434). 

Tellurane dications 159, 160, and 161 were obtained by oxidation of the corresponding tris-chalcogenides 158 with nitrosonium tetrafluoroborate as shown in Equation (44) <1998JA1230> and <1997BCJ2571>. 

Nitrosation. Nitrosonium tetrafluoroborate readily effects the nitrosation of the various polymethylbenzenes and anisoles in a thermal (dark) reaction,246 i.e.,... 

It is known that the nitrosonium cation is a strong oxidant (54). In (55) it was found by multinuclear NMR ( H, 13C, 19F and 14N) that the interaction of nitrosonium tetrafluoroborate with 2,2,6,6-tetramethyl-4-R-piperidine-1 -oxyl radicals 22a-e resulted in formation of 4-R-2,2,6,6-tetramethylpiperidine-l-oxoammonium tetrafluoroborates (Scheme 16). Cations 23a-e could be classified as nitrosonium complexes of biradicals 24a-e. 

Amino- and 4-amino-1,2,4-triazole undergo a reductive dediazoniation to 1,2,4-triazole when treated with nitrosonium tetrafluoroborate in the presence of mesitylene67. 

In Milner s method132 the amine is diazotized with solid nitrosonium tetrafluoroborate in CH2CI2 and, without isolation, the diazonium salt is heated and yields the fluoroarene in good yield. The method is also applicable to aniline derivatives bearing carboxy and hydroxy substituents, compounds which give poor yields in the classical procedure. 

The high performance nitramine explosive known as CL-20 (5) has been synthesized via a two-stage nitrolysis starting from the key intermediate (83). The first stage uses dinitrogen tetroxide or nitrosonium tetrafluoroborate for nitrosolysis. The second step, involving nitrolysis of the acetamide and nitrosamine bonds, is achieved with nitronium tetrafluoroborate (>90 %) or mixed acid at 75 °C to 80 °C (93 %). The synthesis of CL-20 is discussed in more detail in Chapter 6. 

Nitroform, Methanol, Hydrazine Nitroform, Diethyl ether, Hydrazine Nitroform, Methyl acetate, SUver-I oxide, 1,4-Dibromobutyne-2, Chloroform Glyoxal, Benzylamine, Formic acid, Acetonitrile, Acetic anhydride. Palladium on charcoal, Bromobenzene, Chloroform, Sulfolane, Nitrosonium tetrafluoroborate. Ethyl acetate TNT, DMSO, Oxygen gas. Sodium benzoate. Hydrochloric acid. Methanol, Acetone... 

Nitrosonium tetrafluoroborate has been prepared from nitrosyl fluoride (NOF) and boron trifluoride in Freon-113. With this reagent, in a nitro-methane solution, pyridine was converted into jV-nitrosopyridinium tetra-fluorobate, m.p. 155°-158°C [33]. 

Nitrosonium tetrafluoroborate (1) is a white powder made from hydrogen fluoride, boron trifluoride and nitrogen dioxide. 

Nitrosonium tetrafluoroborate reacts with aliphatic azides to yield the corresponding alkyl fluorides.84,85 The yield depends, thereby, on the length of the chain (Table 15). 

By using the same reagent combination of nitrosonium tetrafluoroborate and pyridinium poly(hydrogen fluoride) (PPHF), diarylacetylenes could be converted into diaryltetrafluoro-ethanes in moderate to good yields (Table 19).87... 

Adamantane and other tertiary hydrocarbons have been converted by applying this method [nitrosonium tetrafluoroborate/pyridinium poly(hydrogen fluoride) (PPHF)] into the corresponding fluorohydrocarbons in excellent yields.88... 

Nitrosonium tetrafluoroborate reacts with alkyl sulfilimines (R-N = S = 0) to give alkyl fluoroborates, which are probably precursors of alkyl fluorides, since no water is produced. No further details were reported.190... 

Unsubstituted alkyl azides react with nitrosonium tetrafluoroborate without formation of alkyl fluorides, but azidonitriles give fluoronitriles with this reagent.69 Depending on the chain length, rearrangements can occur extensively. Interaction between the nitrile group and boron trifluoride has been invoked to explain these reactions. 

Direct fluorination of diarylacetylenes to the corresponding tetrafluoroethane derivatives has been accomplished with nitrosonium tetrafluoroborate and pyridinium poly(hydrogen fluoride)520 [Eq. (5.200)]. 

Treatment of some a-ethynyl acetates with a mixture of nitrosyl fluoride and nitrosonium tetrafluoroborate affords bis[(acetoxyalkyl)carbonyl]furoxans the presence of the a-acetoxy group appears to be essential (81JOC312). Monosubstituted furoxans have been obtained by nitrosation of unsaturated hydrocarbons thus the reaction of nitrous acid with p -hydroxycin-namic acid affords 3-(p-hydroxyphenyl)furoxan, its structure being confirmed by X-ray crystallography (80LA1557). 

Despite the reactivity of carbazole cation-radicals, that of 9-ethylcarbazole has been trapped by nucleophiles, e.g., I", NO2,475 Thus, iodo and nitro derivatives of 9-ethylcarbazole result, along with 9,9 -diethyl-3,3 -bicarbazole, when 9-ethylcarbazole is oxidized by iodine in the presence of iodide and nitrite.473 Oxidation in the absence of nucleophiles, e.g., by nitrosonium tetrafluoroborate, permits the synthesis of the cation-radical fluoroborate salts of the 3,3 -bicarbazoles476 The reactivity of the cation-radical of 9-vinylcarbazole has been reviewed recently.11,477... 

Nitrosonium tetrafluoroborate forms birefringent, orthorhombic, hygroscopic platelets, which decompose by water. It may be stored in glass bottles if dry, and is prepared by reacting sodium tetrafluoroborate with dinitrogen trioxide. Nitrosonium tetrafluoroborate is commercially available. 

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