Synthesis via 2-acylmethyl-2-oxazoline.: I.: A novel synthesis of 3-acyl-2-pyridones by Michael addition of 2-acylmethyl-2-oxazoline to α,β-acetylenic ketones

The reaction of the sodium salt of 2-acylmethyl-4,4-dimethyl-2-oxazolines with alpha,beta-acetylenic ketones in ethanol gave Michael adducts, which were easily transformed to 4,6-disubstituted 3-acyl-1-(2-hydroxy-1,1-dimethylethyl)-2-pyridones by silica gel. N-Dealkylation of the pyridones was performed using hydrochloric acid in good yields. Deacylation of the pyridones was performed using potassium hydroxide. A mild treatment of the pyridones with bases or silica gel gave 7-oxa-1-azabicyclo[4.3.0]non-3-en-2-one derivatives via intramolecular Michael addition. A similar reaction of 2-phenacyl-2-oxazoline with diphenylpropynone gave the corresponding 1-(2-hydroxyethyl)-2-pyridone derivative, which was inert against these I-dealkylation, 3-deacylation, and intramolecular addition reactions.