Nucleophilic displacements of N-aryl and heteroaryl groups. Part 3. Pyrylium-mediated synthesis of unsymmetrical diarylamines from anilines

Abstract

2-Ethoxycarbonyl-4,6-diphenylpyrylium salts (1) reacted with various ring-substituted anilines to give the corresponding pyridinium salts (2)(average yield 90%); these were hydrolysed to the pyridinium betaines (3)(75%) and treated with thionyl chloride followed by an aniline to give the amides (4)(70%). Refluxing in toluene with sodium hydride for 12 h transfers intramolecularly the 1-aryl group of the pyridinium salt (4) to the nitrogen of the amide. Aqueous work-up cleaves (6) and the diarylamine is purified by sublimation (60%)(overall yield ca. 30%).