Visible‐Light‐Induced Direct Oxidative C−H Amidation of Heteroarenes with Sulfonamides

Abstract

A direct oxidative C-H amidation of heteroarenes with sulfonamides via nitrogen-centered radicals has been achieved. Nitrogen-centered radicals are directly generated from oxidative cleavage of N-H bonds under visible-light photoredox catalysis. Sulfonamides, which are easily accessed, are used as tunable nitrogen sources and bleach (aqueous NaClO solution) is used as the oxidant. A variety of heteroarenes, including indoles, pyrroles and benzofurans, can undergo this amidation with high yields (up to 92 %). These reactions are highly regioselective, and all the products are isolated as single regioisomer.

Construction and Functionalization of Heteroarenes by Use of Photoredox Catalysis

“…Then, the radical cations originating from the SET oxidation of pyrroles such as 69 served as electrophiles and reacted with the deprotonated sulfonamides. Similar results were obtained by replacing the acridium/O 2 catalytic system by Ir(ppy) 2 (dtbbpy)PF 6 /NaClO …”

Anthraquinones: Versatile Organic Photocatalysts

“…Radical amination of aromatic rings typically requires an expensive inorganic catalyst and derivativization of the amine substrate. [81] Itoh and collaborators developed a cross-dehydrogenative imidation without a transition-metal catalyst or other harsh oxidant that uses 2-tert-butylanthraquinone as photocatalyst (Scheme 28). [82] The catalytic imidation of several indoles 69 under photooxidative conditions was performed with phthalimide (112) to give 3-substituted products 113.…”

Recent Advances in Photocatalytic C–N Bond Coupling Reactions

“…Yu, Zhang and co-workers have developed an oxidative C-H amidation of heteroarenes with sulfonamides that proceeded via an N-centered radical (Scheme 14). 20 With NaClO solution as the oxidant, a variety of heteroarenes including indoles, pyrroles and benzofurans were amidated in up to 92% yield.…”