Lewis Base Catalyzed Synthesis of Multisubstituted 4-Sulfonyl-1H-Pyrazole Involving a Novel 1,3-Sulfonyl Shift

A facile synthesis of highly substituted 4-sulfonyl-1H-pyrazoles from N-propargylic sulfonylhydrazone derivatives has been developed. Allenic sulfonamide formation and 1,3-sulfonyl shift were established to be the critical steps of this transformation.