Nitrilium
A nitrilium ion is a nitrile that has been protonated, [RCNH]+, or alkylated, [RCNR′]+.[1]
Synthesis
Nitriles are only weakly basic[2] and are poor nucleophiles, but they will attack very reactive electrophiles such as carbocations.[3]
Nitrilium salts can be prepared by reacting nitriles with trialkyloxonium salts. The nitrilium ions thus formed can then be reduced to secondary amines with sodium borohydride in diglyme. This is a convenient route to secondary amines of the form RCH2—NH—R′.[4]
As intermediates
Nitrilium ions are believed to be intermediates in the hydrolysis of nitriles,[5] the Beckmann rearrangement, the Friedel-Crafts cyclization of amines to isoquinolines,[6] the Schmidt reaction with ketones,[7] and the Ugi, Ritter, Pinner and Passerini reactions.
References
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- ↑ IUPAC Gold Book: nitrilium ions
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