Abstract
Ring transformations of 2-aryl-6-methyl-4H-1, 3-oxazin-4-ones (1-3) with carbanions derived from various ketones, esters, lactones, and nitriles to give 3-acetyl-4, 5, 6-trisubstituted-2-pyridone derivatives 12 were explored. 1, 3-Oxazin-4-ones (1-3) underwent initial attack of the carbanions at the 2-position of the ring to give the 2-substituted-2-aryl-3, 4-dihydro-2H-1, 3-oxazin-4-ones (9a-o). The dihydrooxazines (9a-g) bearing a quarternary-carbon substituent at the 2-position of the 1, 3-oxazine ring were stable. In contrast, the dihydrooxazines (9h-o) which possess a tertiarycarbon substituent at the 2-position were converted into the ring-opened acetoacetamide derivatives (11) and subsequently recyclized to the corresponding 3-acetyl-2-pyridone derivatives (12).
