A General Approach towards NH‐Pyr­azoles That Bear Diverse Fluoroalkyl Groups by Means of Fluorinated Iminium Salts

A new and general approach to important fluoroalkyl-substituted pyrazoles has been developed. The approach is based on the use of fluoroalkyl amino reagents and their Lewis acid activation to form a fluoroalkyl iminium salt that acts as a formal “fluoroacyl transfer reagent”. Their interaction with readily available fluoroalkyl azines followed by spontaneous cyclization of the formed intermediates under acidic conditions leads to the formation of 3,5-disubstituted pyrazoles. The reaction is extremely versatile, high yielding, and allows quick access to pyrazoles that bear two fluoroalkyl functionalities (identical or different). These compounds are otherwise difficult to prepare. The reaction is scalable and suitable for industrial production.