Iminocarbocation intermediates were in situ-generated by treating various oximes with trifluoromethanesulfonic anhydride (Tf2O) in the presence of triethylamine in toluene and nucleophilic trapping with amines or sodium enolates under mild conditions afforded the corresponding amidines and enamines. Some of the thus-obtained enamines were converted to 2-substituted 4-oxo-3-quinolinecarboxylic acid derivatives by subsequent intramolecular Friedel–Crafts acylation.
The NMR spectra of α-cyano-β-amino-β-alkylacrylic esters prepared from α-cyano-β-methoxy-β-alkylacrylic esters and simple amines have been studied. It has been found that these aminoesters, in a variety of solvents, are all present in an intramolecular hydrogen-bonded enamine form with a chelate ring.
Facile one-pot syntheses of amidines and enamines were achieved by trapping carbocation intermediates that were formed by Beckmann rearrangement of oximes with amines and carbon nucleophiles, respectively, under mild conditions.