Generation and in Situ Acylation of Enaminone Anions: A Convenient Synthesis of 3-Carbethoxy-4(1H)-pyridinones and -4-pyrones and Related Compounds

Article abstract of DOI:10.1021/jo00016a028

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 55-75percent for R groups lacking acidic α or γ protons and ca. 30percent 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.