Substituted 4(5H)-oxazolones and their salts. 3. Synthesis of 4(5H)-oxazolonium salts from amides of 2,4-dihydroxy-3,3-dimethylbutanoic acid

2-Alkyl-substituted 4(5H)-oxazolonium salts were synthesized by the reaction of amides of 2,4-dihydroxy-3,3-dimethylbutanoic (pantoic) acid with aliphatic carboxylic acid anhydrides in the presence of an equimolar amount of perchloric acid. The hydrolysis of these salts was realized. Various acyl derivatives of pantoic acid amides were obtained, and the possibility of their cyclization to give 4(5H)-oxazolonium salts under the influence of condensing reagents was demonstrated. The mechanism of the heterocyclization of pantoic acid amides is discussed on the basis of these results.See [1] for communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 894–900, July, 1981.