Synthesis of 3‐Acetyl‐4‐hydroxy‐1‐phenylpyridin‐2(1H)‐one Derivatives

The cyclization of aryl ketone anilides 3 with diethyl malonate to affords 4-hydroxy-6-phenyl-6H-pyrano[3,2-c]-pyridin-2,5-diones 4 in good yields. 3-Acetyl-4-hydroxy-1-phenylpyridin-2(1H)-ones 5 are obtained by ring-opening reaction of 4-hydroxy-6-phenyl-6H-pyrano[3,2-c]-pyridin-2,5-diones 4 in the presence of 1,2-diethylene glycol. The reaction of 3-acetyl-4-hydroxy-1-phenylpyridin-2(1H)-ones 5 with hydroxylamine hydrochloride produces 4-hydroxy-3-[N-hydroxyethanimidoyl]-1-phenylpyridin-2(1H)-ones 6 from which 3-alkyloxyiminoacetyl-4-hydroxy-1-phenylpyridin-2(1H)-ones 7 are obtained by reacting with alkyl bromides or iodides in the presence of anhydrous potassium carbonate with moderate yields. The similar compounds can be synthesized on refluxing 3-acetyl-4-hydroxy-1-phenylpyridin-2(1H)-ones 5 with substituted hydroxylamine hydrochloride in the presence of sodium bicarbonate with good yields. Most of the synthesized compounds are characterized by IR and NMR spectroscopic methods.