Synthesis of α‐Arylglycosides by Ni‐Photoredox Arylation of Sugars with an Organic Photocatalyst

Herein we report a Ni‐photoredox catalytic methodology for the synthesis of C‐aryl glycosides via arylation of monosaccharides unprotected at the anomeric position. In our work, the iridium‐complex previously employed as photocatalyst in this kind of Ni‐photoredox arylation of alcohols, was replaced by 5CzBN – a readily available donor‐acceptor cyanoarene photocatalyst. Six benzyl protected monosaccharides showed moderate to good reactivity and, in most cases, an excellent selectivity for the α‐C‐aryl glycoside product (α /β ≥ 10:1). Electron‐rich and electron‐poor aryl bromides were found equally suitable for the reaction, affording the corresponding products with comparable yields. Stern‐Volmer experiments and yield trends are supportive of a mechanism involving reductive quenching of the photocatalyst with a sugar‐NHC adduct, generating a glycosyl radical which then enters a Ni‐catalytic cycle.