SYNTHETIC APPLICATIONS OF N-N LINKED HETEROCYCLES .4. REACTION BETWEEN 1-PYRIDINIO-4-PYRIDONE CATIONS AND CYANIDE ION - MECHANISM OF CYANOPYRIDINE FORMATION, AND A REGIOSELECTIVE SYNTHESIS OF 4-CYANOPYRIDINES

The 1-pyridinio-4-pyridone cations (1) give with aqueous sodium cyanide mixtures of 2- and 4-cyanopyridines, 2-cyanopyridine formation being favoured by high cyanide ion concentration, and 4-cyanopyridine formation by low cyanide ion concentration, when small amounts of the intermediate 1,4-dihydro-4-cyano- adducts (7) or (9) are also observed. The 2,6-dimethyl-1-pyridinio-4-pyridone cations (2) in contrast give high yields of the 1,4-dihydro-4-cyano-adducts (8) or (10), the former being decomposed quantitatively by heat to 4-cyanopyridines and 2,6-dimethyl-4-pyridone. Only very small amounts of 2-cyanopyridines are formed. Mechanisms for the two reactions are proposed which account for the experimental observations.