Electrocyclization for the Synthesis of Mono‐ and Disulfonyl‐substituted Pyrazoles From Sulfonyl Hydrazines and 1,3‐Diketones

Abstract The tunable electrocyclic reactions for the synthesis of a series of mono‐ and disulfonyl‐substituted pyrazoles from sulfonyl hydrazines and 1,3‐diketones were investigated by utilizing inexpensive electrolytes under electrochemical conditions in an undivided cell. When n Bu 4 NBF 4 was used as an electrolyte, it afforded monosulfonyl‐substituted pyrazoles. By contrast, when NH 4 I was used as an electrolyte, it gave disulfonyl‐substituted pyrazoles. The mechanistic investigation shows that they all underwent a free radical process but formed N ‐centered sulfonyl hydrazine radical and S‐centered sulfonyl radical in the synthesis of mono‐ and disulfonyl‐substituted pyrazoles, respectively.