Site-Selective <i>O</i>‑Arylation\nof Carbohydrate Derivatives through Nickel–Photoredox Catalysis

Site-selective <i>O</i>-arylations of glycoside-derived\ndiols have been achieved by couplings with bromoarenes upon irradiation\nwith blue LEDs in the presence of an iridium photocatalyst and a nickel\ncomplex. The use of hexamethylenetetramine (hexamine) in place of\nquinuclidine, along with the application of a methoxy-substituted\n2,2′-bipyridine ligand, provided improvements in yield for\nthis relatively challenging substrate class. Selective arylation took\nplace at the less sterically hindered OH group, as determined by the\nsubstitution pattern and configuration of the glycoside substrate.\nPercent buried volume calculations were used to quantify the relative\nlevels of steric hindrance at the two reactive sites.