Nucleophilic displacements of N-aryl and heteroaryl groups. Part 1. Pyrylium-mediated transformation of anilines into phenols

Abstract

Aromatic amines with 2,4-diphenyl-5,6,7,8-tetrahydrochromenylium trifluoromethanesulphonate (5) gave the corresponding pyridinium salts (6;R = aryl) which were converted by base into the anhydrobases (7). Benzoyl chloride converted (7) into the new pyridinium anhydrobases (9). These anhydrobases (9) rearranged at 150 °C into the isomeric phenol enol ethers (10) which were readily hydrolysed to yield the corresponding phenols. The mechanistic and synthetic significance of the results are assessed.