Identification of a Surprising Boronic Acid Homocoupling Process in Suzuki–Miyaura Cross-Coupling Reactions Utilizing a Hindered Fluorinated Arene

Abstract

The Suzuki–Miyaura cross-coupling reaction of 2-bromo-1,3-bis(trifluoromethyl)benzene with arylboronic acids was evaluated and determined to suffer from the formation of large amounts of boronic acid homocoupling products in conjunction with dehalogenation. Homocoupling product formation in this process likely occurs through a rare protonolysis/second transmetalation event rather than by the well-established mechanism requiring the involvement of O2. The scope of this boronic acid homocoupling reaction was investigated and shown to predominate with electron-deficient arylboronic acids. Finally, a good yield of cross-coupling products could be obtained by employing dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine (SPhos) as the ligand.

Metal-Free ortho-Selective C–H Borylation of 2-Phenylthiopyridines Using BBr3

“…14 A homocoupling reaction of 3k in the presence of Pd(OAc) 2 furnished 7 in 45% yield, and the byproduct was 1k. 15 Moreover, the C(sp 2 )−B bond of 3k could also be converted into a C−N bond with morpholine, giving 8 in 48% yield. 13 Sulfones and sulfoxides were important building blocks in organic synthesis.…”

“…Halogenation such as chlorination and bromination of 3k offered the corresponding products 5 and 6 in 57% and 54% yield, respectively . A homocoupling reaction of 3k in the presence of Pd­(OAc) 2 furnished 7 in 45% yield, and the byproduct was 1k . Moreover, the C­(sp 2 )–B bond of 3k could also be converted into a C–N bond with morpholine, giving 8 in 48% yield .…”

Trace amounts of palladium catalysed the Suzuki–Miyaura reaction of deactivated and hindered aryl chlorides

“…An interesting trend was observed during the screening process of ligands: the amounts of homocoupling products and dehalogenation products were similar, regardless of the ligand used (see Table S6 in the ESI †). Based on the previous literature, 35 it was reasonably suspected that these products in this experiment were likely formed through a second transmetalation process.…”

Synthesis and characterization of [4‐{(CH2O)2CH}C6H4]2Hg, [4‐(O=CH)C6H4]2Hg and [(E)‐4‐(RN=CH)C6H4]2Hg (R = 2′‐py, 4′‐py, 2′‐pyCH2, 4′‐pyCH2)

“…Their identity was confirmed by multinuclear NMR and MS studies. While our work was under preparation a report was published [ 51 ] on unexpected boronic acid homocoupling products, including compounds 8 and 9 , formed during Suzuki–Miyaura cross‐coupling reactions of 2‐bromo‐1,3‐(CF 3 ) 2 C 6 H 3 Br with various arylboronic acids, using Pd complexes. Our spectroscopic data fit very well with those reported in this recent article.…”