Reactions of vinyl sulfone with α-diazo-β-ketosulfone and Bestmann-Ohira reagent for the regioselective synthesis of highly functionalized pyrazoles

The 1,3-dipolar cycloaddition of diazomethylsulfone anion, generated in situ from α-diazo-β-ketosulfone, with vinyl sulfone proceeds in a regioselective manner to provide sulfonylpyrazoles. Similar reaction of diazomethylphosphonate anion, derived from Bestmann-Ohira reagent, with vinyl sulfone leads to phosphonylpyrazoles. The sulfonyl group of vinyl sulfone undergoes chemoselective elimination in these reactions.

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