Photoinduced in situ "oxidation" of half-sandwich metal complexes to "high-valent" cationic metal complexes has been used to accelerate catalytic reactions. Here, we report the unprecedented photoinduced in situ "reduction" of half-sandwich metal [Rh(III)] complexes to "low-valent" anionic metal [Rh(II)] ate complexes, which facilitate ligand exchange with electrondeficient elements (diboron). This strategy was realized by using a functionalized cyclopentadienyl (Cp A3 ) Rh(III) catalyst we developed, which enabled the basic group-directed room temperature ortho-C−H borylation of arenes.

The lateral π-extension of helicenes would yield interesting physical properties derived from the enhanced π-stacking ability as well as intrinsic helical chirality. Here we report the regiodivergent synthesis of hexabenzocoronene (HBC)-based [6]helicenes via cationic rhodium(I)/segphos complex-mediated intramolecular [2 + 2 + 2] and [2 + 1 + 2 + 1] cycloadditions of triynes followed by Scholl reaction. The resulting HBC-based[6]helicenes possess stable helical chirality but more planar structure than previously reported HBC-based [7] and [9]helicenes. Therefore, these HBC-based [6]helicenes exhibit πstacking-induced chiral self-recognition in solution, allowing the measurement of enantiomeric ratios by 1 H NMR spectroscopy without any chiral additive.

The 1,3-diethoxycarbonyl-2,4,5-trimethylcyclopentadienyl (CpE) rhodium(III) complex displayed high efficacy in the catalytic oxidative annulation of 1-naphthols with internal alkynes under mild conditions. DFT calculations revealed that lower activation energies for the...