Unusual ring transformation of 2-halogeno-N-phenacylpyridinium salts in reaction with secondary amines: a facile ‘one-pot’ route to 1-amino-4-(oxazol-2-yl)butadienes

Chemistry of heterocyclic compounds at the Department of Organic Chemistry, Chemical Faculty, M. V. Lomonosov State University. (Review)

“…The reaction takes place for 2-chloropyridinium salts [134,135] and also for the 2-methylthio [136] and 2-phenoxy [137] derivatives. This method has found widespread use for the production of azoles.…”

Formation of oxazoles from 2-methylsulfanyl-N-phenacylpyridinium salts

“…5a The mass spectrum of product 5a exhibits the most intensive peak at m/z = 195 (loss of the piperidine fragment, M-C 5 H 10 N),which is typical for 2-(4-amino-1,3-butadienyl[1,3]oxazoles. 7 We suppose that the conversion of the pyridinium salt 4 to oxazoles 5 is initiated by piperidine causing deprotonation and convertion of the salt 4 to the enol betaine 6; this …”