Nitrosyl fluoroborate

The reaction of acylsilanes with acid chlorides in the presence of A1C13 leads to furans (Table 9.41) [45]. In these reactions an acyl cation initiates the addition with ensuing silyl migration yielding an intermediate vinyl cation. Attack of the carbonyl oxygen followed by proton loss affords the observed products (Scheme 9.16). An analogous reaction with nitrosyl fluoroborate provides a route to oxazoles (Table 9.42) [65]. The nitrosyl cation serves as the electrophile in this application. 

Table 9.42 Synthesis ofisoxazoles from nitrosyl fluoroborate and allenylsilanes.

High-purity nitrogen oxide trifluoride has been obtained by fluorolysis of the nickel salt. By first forming this compound, troublesome impurities such as carbon tetrafluoride (from the fluorine) and nitrous oxide (from the nitric oxide) are avoided. The mixture, with nitrosyl fluoride and some nitryl fluoride, is purified chemically by titrating the gas with boron trifluoride, when both of the strongly basic oxyfluorides are removed as fluoroborates ... 

Alkylation of thioamides with Meerwein s reagent (trialkoxonium fluoroborate) proceeds via a thioiminoester and subsequent base hydrolysis with sodium carbonate (equation 32). For the synthesis of 2-pyridones from 2-thiopyridones, chloroacetic acid has been used. ° Mild reaction conditions are provided by nitrosyl species which are derived from a variety of reagents excess NaNOa/HCP in aqueous medium, nitrosonium tetrafluoroborate in dichloromethane, dinitrogen tetroxide in acetonitrile at low temperature and f-butyl thionitrate. ... 

Lead (IV) acetate azides. Nitrosyl tetra-fluoroborate. Sulfur dichloride. 

Nitrosyl fluoride, FNO. Of several methods for the preparation of this highly reactive gas reviewed by Andreades, that preferred by du Pont workers is pyrolysis of a mixture of nitrosyl fluoroborate and sodium fluoride. BoswelP of du Pont found that, when a stream of gas generated in this way was passed into a solution of cholesteryl acetate in methylene chloride at 0°, the solution turned deep blue and workup afforded the 5a-fiuoro-6-nitrimine (2) in high yield. This was hydrolyzed by neutral... 

Deamination Aryidiazonium hexafluorophosphates. Aryldiazonium tetrahaloborates. Di-fluoroamine. Dinitrogen tetroxide (White). Hydroxylamine-O-sulfonic aeid. Hypophos-phorous acid. 3-Nitro-N-nitrosocarbazole. Nitrosyl chloride. Tetramethylurea. Debenzylation of benzoylamines Triethyloxonium fluoroborate. 

Nitrous acid (3), which is generated from sodium nitrite and aqueous acid, undergoes dehydration under the acidic conditions to form nitrosyl cation 4. Reaction of 4 with the aryl amine eventually affords the aryl diazonium salt after tautomerization and dehydration. The addition of fluoroboric acid sets the stage for the second step leading to aryl fluoride. 

C. CARB0NYL(7 -C YCLOPENTADIEN YL) NITROSYL-(TRIPHENYLPHOSPHINE)RHENIUM(I) TETRA-FLUOROBORATE(l -)... 

Nitrosyl(1,4,8,11-tetrathiacyclotetradecane)rhodium(III) Tetra-FLUOROBORATE, [Rh(TTP)NO] (BF4)o. To a solution of 0.25 g [Rh(TTP)]-BF4 in 40 ml acetonitrile, a solution of 0.1 g (excess) nitrosonium tetra-fluoroborate (Aldrich) dissolved in 5 ml acetonitrile was added drop-wise. During the addition, the solution turned from the golden color of [Rh(TTP)] to a bright green. The volume of the solution was then reduced to approximately 10-15 ml, and small aliquots of diethyl ether were added for 30 min. The bright green microcrystalline product was collected, washed with diethyl ether, and dried by pumping on a vacuum line. 

Nitrosyl fluoroborate may be stored in glass bottles. Used to prepare NOF. 

Nitrosyl fluoroborate Reactions with nitrosyl salts Diazonium salts from azomethines... 

N-Benzylideneaniline treated with an equivalent amount of nitrosyl fluoroborate in acetonitrile -> benzenediazonium fluoroborate. Y almost 100%. Also formation of carbonium ions by reaction of nitrosyl fluoroborate with azides s. M. P. Doyle and W. Wierenga, Am. Soc. 92, 4999 (1970). 

Nitrosyl fluoroborate Acids from amides at low temp, in organic solvents Carboxylic and sulfonic acids... 

A soln. of crude cyclohexyl trimethylsilyl ether and triphenylcarbonium fluoroborate in methylene chloride stirred 9 hrs. at room temp, under Ng cyclohexanone. Y 92%. - This is part of a 2-step mild oxidation of alcohols to oxo compds. in high yields. F. e. s. M. E. Jung, J. Org. Chem. 41, 1479 (1976) with nitrosyl fluoroborate, also oxidation of alkoxystannanes, and direct oxidation of alcohols, s. G. A. Olah and T.-L. Ho, Synthesis 1976, 609. 

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