Lewis acid‐mediated defluorinative [3+2] cycloaddition/aromatization cascade of 2,2‐difluoroethanol systems with nitriles

Abstract The properties of C−F bonds, including high thermal and chemical stability, make derivatization of organic fluorine‐containing compounds by the activation of the C−F bond and subsequent functionalization quite challenging. We herein report a Lewis acid‐mediated defluorinative cycloaddition/aromatization cascade of 2,2‐difluoroethanols with nitriles as a novel synthetic method for the preparation of 2,4,5‐trisubstituted oxazoles. This reaction, which involves cleavage of two C−F bonds and the consecutive formation of C−O and C−N bonds in a one‐pot fashion, features a broad substrate scope and moderate to high reaction yields. Mechanistic studies revealed that the reaction is initiated by the Lewis acid‐mediated ring closure of the 2,2‐difluoroethanol to produce the fluoroepoxide intermediate. magnified image