Heptafluorotolyl-substituted perfluorocyclopentene acts as a four-electron oxidant for the homocoupling of Grignard reagents. It can also be used for catalytic homocoupling with a low catalyst loading (up to 2 mol %) in the presence of atmospheric oxygen. The organocatalytic cycle involves the generation of an organic radical and a perfluorocyclopentadienyl anion.

Highly electron-poor SPhos ligands bearing either 2,6-bis(trifluoromethyl)-4-pyridyl (BFPy) or 3,5-(CF3)2C6H3 groups were synthesised. The former ligand highly accelerated the Pd-catalysed direct arylation of 2-propylthiophene, 2-methylthiophene or benzo[b]thiophene with only 1 mol% of the catalyst. This high catalytic activity can be attributed to a combination of electronic properties and the secondary Pd–arene interaction of BFPySPhos. The secondary interactions of SPhos, PhSPhos and BFPySPhos were optimised at the oniom(mp2/lanl2dz:b3lyp/lanl2dz) level and were further evaluated using the NBO method by DFT at the M06-2X/6-31G(d) level with LanL2DZ + ECP. The deletion energy analysis showed that the transfer of electrons from Pd to aromatic ring is the dominating factor for the secondary Pd–arene interaction of SPhos–Pd0 complexes. Although an electron-poor BFPySPhos does not particularly favour this type of interaction, this interaction is still substantial enough to sufficiently stabilise the BFPySPhos–Pd complex.

•Evaluation of the shielding effect of fluoroaromatics by nucleus-independent chemical shift (NICS) technique.•Calculations of NICS values at more than 3.5 Å above the aromatic ring.•Correlation of chemical shifts between theoretical and experimental values.The shielding effect of fluoroaromatics on nuclei was estimated using nucleus-independent chemical shift (NICS) calculations at the GIAO/B3LYP/6-311++G(2d,p) level. The strengths of diamagnetic contributions of hexafluorobenzene at more than 3.5 Å above the ring center were estimated to be ca. 0.73 times those of benzene. The chemical shift of a proton located above the fluoroaromatic ring is shifted upfield owing to such a relatively weak shielding effect of fluoroaromatic; we demonstrated that in 1H NMR measurement on BINAP bearing C6F5 groups.The shielding effect of fluoroaromatics in NMR was studied using nucleus-independent chemical shift (NICS). The upfield shift of the proton in 1H NMR due to the shielding effect of the adjacent C6F5 group was also demonstrated experimentally and theoretically.

Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds was achieved at temperatures below 0 °C using a Rh/MeO-F12-BIPHEP catalyst. The reaction of cyclohexenone or N-R-maleimide with arylboronic acids proceeded even at −80 °C in the presence of the Rh catalyst. In the latter case, high enantioselectivity was observed because a low-temperature method was used, regardless of the type of substituent on maleimide.

Highly electron-poor SPhos ligands bearing either 2,6-bis(trifluoromethyl)-4-pyridyl (BFPy) or 3,5-(CF3)2C6H3 groups were synthesised. The former ligand highly accelerated the Pd-catalysed direct arylation of 2-propylthiophene, 2-methylthiophene or benzo[b]thiophene with only 1 mol% of the catalyst. This high catalytic activity can be attributed to a combination of electronic properties and the secondary Pd–arene interaction of BFPySPhos. The secondary interactions of SPhos, PhSPhos and BFPySPhos were optimised at the oniom(mp2/lanl2dz:b3lyp/lanl2dz) level and were further evaluated using the NBO method by DFT at the M06-2X/6-31G(d) level with LanL2DZ + ECP. The deletion energy analysis showed that the transfer of electrons from Pd to aromatic ring is the dominating factor for the secondary Pd–arene interaction of SPhos–Pd0 complexes. Although an electron-poor BFPySPhos does not particularly favour this type of interaction, this interaction is still substantial enough to sufficiently stabilise the BFPySPhos–Pd complex.