On the Reaction of Nitrilium Salts with Secondary Carboxamides

Nitrilium salts 1 , the first products of the Beckmann rearrangement of oximes, react with secondary amides 2 , the final products of this rearrangement, to afford mixtures of up to four different N ‐acylamidinium salts 3–6 (mechanism Scheme 4 ). The ratio 3/4/5/6 depends on the configuration of 2 , the substituents of 1 and 2 , the reaction temperature and the concentrations of the reactants. With tertiary amides nitrilium salts give only one N ‐acylamidinium salt, the formation of which is also explained by the mechanism of Scheme 4 . An X‐ray structural analysis in reported for the product obtained from 2‐pyridone and N ‐isopropylbenzonitrilium hexachloroantimonate. First cyclic nitrilium salts ( 1d, k, w ) were prepared.