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

Herein, starting with propiolates and sulfonyl hydrazides, we developed a concise and facile synthesis of 2-sulfonylated chromeno [4,3-c]pyrazol-4(2H)-ones or 2,5-dihydro-4H-pyrazolo[4,3-c]quinolin-4-ones via 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.