Exercise in 1-aryl-3-CF3-1H-pyrazoles: regioselective synthesis of 4-/5-iodides and cross-coupling reactions

Abstract

A series of 1-aryl-3-CF₃-1H-pyrazoles was prepared and examined using iodination reactions. Treatment with n-BuLi followed by trapping of the corresponding lithium pyrazolide with elemental iodine produced 5-iodo derivatives exclusively, while CAN-mediated iodination with I₂ afforded isomeric 4-iodides in a highly regioselective manner. The title iodides were demonstrated to be convenient building blocks for the preparation of more complex 3-trifluoromethylated pyrazoles through the model Suzuki–Miyaura and Sonogashira reactions.