Ultrasound-Assisted Remote Benzylic C(sp3)–H Alkylation of N-Fluoroamides with Enol Silanes

We have developed an ultrasound-assisted remote benzylic C(sp³)-H alkylation of N-fluorobenzamides with enol silanes; a series of β-aryl substituted propiophenones was generated in good to high yields. This reaction represents a formal C(sp³)-C(sp³) coupling and features simplicity, high efficiency, and wide substrate scope in a multiple-step sequential process, which involves N-F homolysis, 1,5-hydrogen atom transfer, benzylic radical addition, oxidation by copper(II) salt, and removal of the trimethylsilyl group. Also, DFT theoretical calculations and Marcus theory were employed to consolidate the proposed reaction mechanism.