Synthetic applications of N-N linked heterocycles. Part 7. The preparation of 4-alkyl- and 4-aryl-pyridines by regiospecific attack of Grignard reagents ? to quaternary nitrogen in N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium salts

Abstract

N-(2,6-Dimethyl-4-oxopyridin-1-yl)pyridinium salts (4), new reagents for the regiospecific synthesis of 4-substituted pyridines, give moderate to high yields of 4-alkyl- and 4-aryl-pyridines (8)–(10) on reaction with Grignard reagents. The scope and limitations of the reaction, which proceeds via 1,4-dihydro-intermediates (5)–(7), are explored. No 2-substituted pyridines were detected. Some reactions with organolithium compounds are also described.