Probing B–X to B–H conversions and applications in C–F bond activation catalysis

Herein we exploit a catalytic amount of [Ph3C]+ to initiate B-X to B-H bond conversion with Et3SiH. This was applied to 6 haloboranes. However, 9-X-9-borabicyclo[3.3.1]nonane (B-X-9-BBN, X = F, Br) reacts directly with silane. Thus, C-F bond activation of benzyl fluorides in the presence of arenes afforded the Friedel-Crafts (FC) products using B-H-9-BBN in the presence of Et3SiH. This catalysis was probed with a range of arenes and several benzyl fluoride derivatives. The protocol is simple, cheap and a convenient route to 1,1-diarylmethanes from benzyl fluorides in good to excellent yields (up to 99%) under mild conditions.