Solvent-Dependent Reactions for the Synthesis of β-Keto-Benzo-δ-Sultone Scaffolds via DBU-Catalyzed O-Sulfonylation/Intramolecular Baylis-Hillman/1,3-H Shift or Dehydration Tandem Sequences

We have developed a solvent-dependent method for the synthesis of novel benzo-delta-sultone scaffolds. A variety of benzylbenzo[e][1,2]oxathiin-4(3H)-one-2,2-dioxides were obtained in high yields in DMF using a one-pot, DBU-catalyzed condensation of 2-hydroxybenzaldehydes with a number of (E)-2-phenylethenesulfonyl chlorides. On the other hand, the initially prepared 2-formylphenyl-(E)-2-phenylethenesulfonate derivatives underwent DBU-catalyzed reactions to a series of 3-[methoxy(phenyl)methyl]benzo[e][1,2]oxathiine-2,2-dioxides in moderate to good yields in MeOH. These reactions presumably proceed via DBU-catalyzed O-sulfonylation/intramolecular Baylis-Hillman/1,3-H shift or dehydration tandem sequences, respectively.