Reinvestigating the Synthesis and Characterization of Ethyl 3-[5-(2-Ethoxycarbonyl-1-methylvinyloxy)-1-methyl-1H-indol-3-yl]-but-2-enoate

We reinvestigated the reported method for the synthesis of ethyl 3-[5-(2-ethoxycarbonyl-1-methylvinyloxy)-1-methyl-1H-indol-3-yl]-but-2-enoate (MIBE), which was obtained by the reaction of 5-hydroxy-1-methyl-1H-indole with excess ethyl acetoacetate catalyzed by indium(III) chloride. Based on the NMR and MS data, we assigned the structure of the isolated product as (3E)-3-(2-ethoxy-2-oxoethylidene)-1,2,3,4-tetrahydro-7-hydroxy-1,4-dimethylcyclopent[b]indole-1-acetate (2a) rather than the reported MIBE.