Synthesis and reactions on Naryl-2-pyridones

ABSTRACT

Previous works showed that 2-[lH]-pyridones do not undergo the ordinary reactions of carbonyl compounds. When benzalaceto phenone [I] reacted with cyanoacetanilide [II] in presence of ammonium acetate three products were obtained which corresponded to IV, V and VI[1-3]. The synthesis of pyridine derivatives by the condensation of ethyl cyanoacetate with unsaturated ketones in the presence of excessive ammonium acetate was reported. The present paper reports on the synthesis of l-aryl-2-pyridones by the reaction of cyanoacetanilide [I] and chalcone [II] in the presence of ammonium acetate at 160-170 degree, to give three products 3-cyano-2 [l-phenyl]-2-pyridones [IV], 3-cyano-2 [1-phenyl] piperidones [Va-c] and 2-amino-4,6-diphenyl nicotinoanilides [Vla-c]. The reactants undergo Michael addition, followed by cyclization to form tetrahydropyridone derivative [III] which is dehydrogenated into pyridone [IV] at the expense of another pyridone molecule [III] which is, of necessity, reduced into the corresponding hexahydro derivative [V] [c.f. scheme A]