DERIVATIVES AND REACTIONS OF GLUTACONALDEHYDE-XIII. REGIOSPECIFIC RING OPENING OF 3-SUBSTITUTED PYRIDINES

Article abstract of DOI:10.1016/S0040-4020(01)88892-X

A number of nucleophilic ring openings of 3-substituted pyridinium salts have been reinvestigated and summarized.The structure of the resulting stable glutaconaldehyde derivatives was investigated in detail by 1H NMR.It has been concluded that in general nucleophilic pyridinium ring openings are highly regiospecific.In each case investigated to date a single product was isolated, as a result of attack by the nucleophile at only one of the pyridine α-positions.With the OH ion as the only nucleophile, attack occurs at the pyridine C-2, while larger nucleophiles such as amines and carbanions attack at the pyridine C-6.This was found to be the case for a variety of 3-substituted pyridines such as 3-methyl-, 3-methoxy-, 3-cyano-, 3-chloro-pyridine.