A convenient synthesis of alkynylpyrazoles

Abstract

Diazomethane add to the enyne sulfones 1, 3, 4, 6–11 regio- and stereo-selectively to give the 4-alkynyl-5-phenylsulfonyl-4,5-dihydro-3H-pyrazoles 12–15 and 17–19, which are converted by MeLi into the 4-alkynyl-1H-pyrazoles 24, 25, 16, 26, 28, 30 in good yields. 4,5-Bis(alkynyl)-1H-pyrazoles 34, 37 are also obtained by the same procedure.