An unexpected Pummerer rearrangement in the synthetic route to ethyl (2′-hydroxy-4′,5′-methylenedioxyphenyl)acetate: An alternative approach to 2,3-dimethylthio benzofurans

[Display omitted] •A structural fragment of the antihyperglycemic coumarin subcoriacin is synthesized.•The CuCl2 catalyzed hydrolysis of the vinylic dithio derivative affords the ester.•An unexpected Pummerer reaction proceeds in the absence of CuCl2 in the hydrolysis.•This last finding provides an alternative approach to 2,3-dithiomethylbenzofurans. The synthesis of ethyl (2′-hydroxy-4′,5′-methylendioxophenyl)acetate, a fragment of the antihyperglycemic natural coumarin subcoriacin, is reported. We found an expeditious route to the title compound in five steps. Final metal catalyzed acid ethanolysis of the vinylic 1,1-methylthio methylsulfoxide derivative afforded the required aryl acetic ester, but in the absence of metal catalyst, an unexpected Pummerer rearrangement produced the 2,3-dimethylthiofuran derivative as the major product. This last result provides an alternative entry to 2,3-dimethlythiobenzofurans.