Covalent amination. Substituent effects on the site of addition of ammonia to quaternized pyridines and pyrazines

1,3-Disubstituted pyridinium ions react completely at about -40 "C with ammonia to give covalent amination products. Addition occurs at C-6 when the C-3 group is CONH2, C02CH3, CF3, or COCH3. Addition at C-2 results when the 3 substituent is C1 or I, and a mixture is found for the 3-CN compound. Parent 1-methyl- and l-benzylpyridinium ions do not yield 2 adducts unless powdered KOH is added to neutralize ammonium ion. 1-Methoxypyridinium ions at -50 "C give adducts which open to 5-amino-2(cis),4(trans)-pentadienalo xime 0-methyl ether. 1-Methyl-3-substituted pyrazinium ions react at the 2 position when the substituent is C1 or CH30 and at the 6 position in the CONHz case. 1-Methylpyrazinium ion first forms a 2 adduct and then a 2,3 diadduct.