Regioselective PyrazoleSynthesis via Base-Mediated[3+2] Cycloaddition of 2‑Alkynyl-1,3-Dithianes and Sydnones

We present a novel base-mediated [3+2] cycloaddition for the regioselective synthesis of polysubstituted pyrazoles using 2-alkynyl-1,3-dithianes and sydnones. By exploiting the umpolung and nucleophilic properties of 2-alkynyl-1,3-dithianes, this method achieves efficient pyrazole construction under mild conditions with excellent regioselectivity, broad functional group tolerance, and diverse substrate compatibility. Furthermore, the unique reactivity of the dithianyl group enables facile derivatization and synthesis of highly functionalized pyrazoles.