Cu()-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- c ]pyrazol-4(2 H )-ones or 2,5-dihydro-4 H -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. A concise and facile synthesis of 2-sulfonylated chromeno [4,3- c ]pyrazol-4(2 H )-ones and 2,5-dihydro-4 H -pyrazolo[4,3- c ]quinolin-4-ones via Cu( ii )-promoted oxidative cascade C-C/C-N bond formation is described.