Fluoroborate, nitrosyl sodium

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... 

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. ... 

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. 

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