A versatile new synthesis of quinolines and related fused pyridines. Part 12. A general synthesis of 2-chloropyridines and 2-pyridones

Abstract

The Vilsmeier formylation of tertiary and secondary enamides leads to 2-pyridones and 2-chloropyridines, respectively. The reaction appears to be quite general allowing substitution in the 1-, 3-, 5-, or 6-position or combinations of these. The major limitation arises with enamides which are unsymmetrically substituted on the double bond with alkyl groups, when mixtures can result. Attempts to introduce a 4-substitutent by a variation of the Vilsmeier reagent had limited success.