The reaction of (chlorocarbonyl)phenyl ketene with enaminones: A novel synthesis of some 5‐acyl‐4‐hydroxy‐2‐(1 H )‐pyridinones and 7‐hydroxy‐5‐oxo‐1,4‐diazepin derivative

A series of substituted 5‐acyl‐4‐hydroxy‐2‐(1 H )‐pyridinone derivatives has been prepared in a one‐step procedure from condensation of (chlorocarbonyl)phenyl ketene with some enaminones which were prepared from 1,3‐diketones, such as 2,4‐pentanedione, 1‐phenyl‐1,3‐butanedione, and ethyl acetoacetate in boiling toluene as a solvent. A mechanism is presented to account for the formation of the products. The overall sequence provides a simple and efficient route to prepare 3,4,5,6‐tetrasubstituted 2‐(1 H )‐pyridinone in good to excellent yields and in a short experimental time. J. Heterocyclic Chem., (2009).