A C-13 study of the reaction of 2,4,6-triarylpyrylium cations with amines

Article abstract of DOI:10.1016/S0040-4020(01)83134-3

The reaction of primary and secondary amines with 2,4,6-triarylpyryliums is shown by C-13 NMR to proceed by fast ring opening to a vinylogous amide; in the case of primary amines this closes slowly to a pyridinium salt. The reaction in DMSO gives the pyridinium salt quantitatively when 2 moles of amines are used, with less amine significant quantities of a diketone intermediate are produced which results in slower conversion.