Iodine‐Catalyzed Ring Opening of 1,1‐Diacylcyclopropanes for Synthesis of Fully Substituted Pyrazole Derivatives

An iodine‐catalyzed [3+2] cycloaddition/ring opening reaction of 1,1‐diacylcyclopropanes with sulfonyl hydrazides has been reported. In the presence of 20 mol‐% iodine, a range of structurally diverse fully substituted pyrazoles with a hydroxy functional group are obtained in moderate to excellent yields with extremely high regioselectivity.