Synthesis of triarylmethanes by silyl radical-mediated cross-coupling of aryl fluorides and arylmethanes†
Although the cross-couplings of aryl halides with diarylmethanes are mostly achieved by transition-metal catalysis, aryl fluorides are rarely used as coupling partners owing to the high inertness of C–F bonds. Herein, we describe the efficient silylboronate-mediated cross-coupling reaction of aryl fluorides with arylalkanes under transition-metal-free, room-temperature conditions. The combination of silylboronate and KOtBu is critical for driving a radical process via the cleavage of C–F and C–H bonds in two appropriate coupling precursors, resulting in a cross-coupling product. This practical cross-coupling protocol is applicable to a wide variety of aryl fluorides with a C(sp2)–F bond. This method can be extended to other coupling partners with a C(sp3)–H bond, including diarylmethanes, diarylethanes, and monoarylalkanes. Many di- and triarylalkanes with tertiary or quaternary carbon centers can be obtained easily in moderate to high yields. We believe that the developed silylboronate-mediated cross-coupling method is a valuable contribution to C–F and C–H activation chemistry.