Cu(II)-Mediated aerobic oxidative synthesis of sulfonated chromeno[4,3-]pyrazol-4(2)-ones.

Herein, starting with propiolates and sulfonyl hydrazides, we developed a concise and facile synthesis of 2-sulfonylated chromeno [4,3-]pyrazol-4(2)-ones or 2,5-dihydro-4-pyrazolo[4,3-]quinolin-4-ones Cu(II)-promoted oxidative cascade C-C/C-N bond formation. This protocol has the advantages of atom economy and good functional group tolerance. The primary mechanism studies indicate that the reaction involves a free-radical process as well as terminal alkyne C-H activation.