Pd-Catalyzed Site-Selective Defluorinative Etherification between Unactivated Perfluoroarenes and Hydrobenzoxazoles.

Abstract

Polyfluoroaryl ethers represent an important framework of biologically active molecules and materials. Owing to the strong bond dissociation energy of C-F bond, selectivity and other issues, transition metal-catalyzed synthesis of polyfluoroaryl ethers from perfluoroarenes via the activation of C-F bond is challenging and underdeveloped, as compared to the well-documented C-O bond formation starting from aryl iodides, aryl bromides or aryl chlorides. Herein, an unprecedented Pd-catalyzed defluorinative etherification for the synthesis of polyfluoroaryl ether skeletons using hydrobenzoxazoles as phenol surrogate, has been reported. The substrate scope for this protocol is broad, with respect to hydrobenzoxazoles and perfluoroarenes, under mild reaction conditions. More importantly, challenging alkenyl and alkynyl substituted polyfluoroarenes could be successfully used as the coupling component for Pd-catalyzed etherification reaction. Density functional theory (DFT) calculations were employed to investigate the reaction mechanism, which suggested that oxidative addition between polyfluorobenzene and Pd(0) constituted the ratedetermining step.