GENERATION AND INSITU ACYLATION OF ENAMINONE ANIONS - A CONVENIENT SYNTHESIS OF 3-CARBETHOXY-4(1H)-PYRIDINONES AND 3-CARBETHOXY-4-PYRONES AND RELATED-COMPOUNDS

Treatment of 2-[(dimethylamino)methylene]-3-oxobutanoates 9 or 10 with LiN(SiMe3)2 in the presence of RCOCl results in C-acylation. The resulting intermediate, without isolation, may be converted to 6-R 3-Carbethoxy-4-pyrones (e.g., 12) by H3O+ or to the corresponding pyridinones (e.g., 13) by NH4OAc. Typically, yields are 55-75% for R groups lacking acidic alpha or gamma protons and ca. 30% for R = Me2CH or MeCH = CH. Replacing 9 with MeCOC(= CHNMe2)SCH2Ph (from MeCOCH2SCH2Ph and Me2NCH(OMe)2 similarly affords 3(PhCH2S)-substituted products such as 29. Alkylation of the pyridinone anions produces mixtures of N- and O-substituted compounds, with the latter predominating; aminolysis of the isolated pyrones (R'NH2-HOAc, where R' = alkyl, Ar, HO, etc.) is the preferred route to the 1-R'-substituted pyridinones.