Photochemical Synthesis of S,N,O-Containing Polyheterocycles via an α-C(sp³)–H Functionalization/Radical Cyclization Cascade

Abstract

A highly effective approach based on an organophotocatalytic α-C­(sp3)–H functionalization/radical cyclization cascade has been developed. This method enables the synthesis of various tricyclic heterocycles containing S, O, and N atoms with excellent site selectivity and diastereoselectivity. Mechanistic investigations have confirmed that the reaction involves photoredox-triggered C­(sp3)–H cleavage followed by a radical cyclization and aromatization process. These findings are expected to pave the way for developing cost-effective tandem radical reactions and synthesizing heterocyclic drugs.

Photoredox catalytic aminomethylation of sulfonylthiazoles

“…SCE, E 1/2 (PS*/PS − ) = +1.35 V vs . SCE], 20 we were delighted to isolate the desired aminomethylation product of benzothiazole ( 3aa ) in 85% yield with 2 mol% of 4CzIPN as a photosensitizer in the presence of K 2 CO 3 in acetonitrile under blue LED irradiation (Table 1, entry 1). Controlled experiments showed the necessity of photosensitizer, base, and light irradiation (Table 1, entries 2–4).…”

Photoredox-Catalyzed Divergent Radical Cascade Annulations of 1,6-Enynes via Pyridine N-Oxide-Promoted Vinyl Radical Generation

“…The development of new radical cascade reactions that could convert readily available chemicals to complex polycyclic frameworks under mild reaction conditions, e.g., metal-free conditions, continues to be an appealing and demanding area of research . Herein, we report organophotoredox-catalyzed divergent vinyl radical-mediated cascade annulations of 1,6-enynes (Scheme ).…”