Concise Synthesis of 3-Acetoxy-N,N-dialkylbenzo[b]thiophene-2-carboxamides from 2-Ethylsulfanylbenzoates

A convenient method for the synthesis of 3-acetoxy-N,N-dialkylbenzo[b]thiophene-2-carboxamides has been developed in three steps from 2-ethylsulfanylbenzoates using an interrupted Pummerer reaction of N,N-dialkyl-3-(2-ethylsulfinylphenyl)-3-oxo-propanamides. Thus, treatment of these sulfinyl amides, prepared by the reaction of 2-ethylsulfanylbenzoates with lithium enolates of N,N-dialkylacetamides followed by oxidation of the resulting N, N-dialkyl-3-(2-ethylsulfanylphenyl)-3-oxopropanamides with sodium metaperiodate and acetic anhydride at 100 degrees C leads to the formation of the desired benzo[b]thiophenes.