Reaction of Acylketene<i>S,N</i>-Acetals with Malonyl Chloride: Synthesis of Novel 1,5-Substituted 4-Hydroxy-6-methylthio-2 (1<i>H</i>)-pyridones and 6,8-Substituted 4-Hydroxy-7-methylthio-2,5-dioxo-5,6-dihydro-2<i>H</i>-pyrano [3,2-<i>c</i>] pyridines

Abstract

The acylketene S,N-acetals 1 react with one equivalent of malonyl chloride in the presence of triethylamine to give novel 1,5-substituted 4-hydroxy-6-methylthio-2(1H)-pyridones 3 in good yields. However, in the presence of excess of malonyl chloride (three equivalents), the reaction proceeds further to give the corresponding pyrano[3,2-c] pyridones derivatives 4 in moderate yields.