The Chemistry of the N-Methyl-3-dehydropyridinium Ylid

The reaction of atomic carbon with N -methylpyrrole, 5b, at 77 K generates the N -methyl-3-dehydropyridinium ylid, 6b, which can be trapped with added hydrogen halides or CO 2 . The addition of CO 2 is strong evidence for the ylid 6b rather than cumulene 7 . Deuterium and 13 C labeling studies demonstrate that 6b rapidly rearranges to the N -methyl-2-dehydropyridinium ylid, 13, by an intermolecular mechanism. Ylid 13 can be trapped with added acids or with O 2 to form 1-methyl-2-pyridone.