An elegant synthesis of alkyl thiochromano[2,3-c]pyrrole-9-carboxylate derivatives utilizing benzo[b]thiofuran-2,3-dione, maleimides and alkanols/water

A novel set of thiochromano[2,3-c]pyrrolidine-1,3-diones incorporating α-hydroxy esters and their acids at C-9 locus, is prepared via direct interaction involving benzo[b]thiofuran-2,3-dione, maleimides and alkanols / H2O at 90 °C. Structures of the new product were deduced from HRMS and NMR spectral data, and confirmed by single-crystal X-ray crystallography. An insight into a proposed pathway involving sequential Michael conjugate addition (as initiated by the sulfur atom) and aldol type reaction is presented herewith.