Preparation of New Nitrogen-Bridged Heterocycles. 55. Reinvestigation of the Bromination/Dehydrobromination of Ethyl 3-[2-(Methylthio)indolizin-3-yl]acrylate Derivatives
bromination/dehydrobromination reactions of ethyl 3-[1-alkoxycarbonyl-2-(methylthio)indolizin-3-yl]acrylates were reinvestigated. Reactions of the title compounds with two equivalents of bromine, followed by heating of the resulting reaction mixture and then treatment with a base gave the unexpected dialkyl 7-bromothieno[2,3-b]indolizine-2,9-dicarboxylates, while similar reactions using benzyltrimethylammonium