Endo/Exo-Controllable Photocyclization by EnT-SET-Switch

Abstract

CBZ6, a redox-neutral non-donor–acceptor-type organo-photocatalyst, presents a strong reductive potential with an oxidative potential of −2.16 V (vs SCE). It can work as a photosensitizer for both single-electron transfer and triplet energy transfer processes. This feature enables site-selective control in the intramolecular hydroarylation of acrylamides. Both 5-exo-trig and 6-endo-trig cyclization products could be prepared regiospecfically under mild conditions. No transition metal, halogen-containing reagents, or additional reductant or oxidant is involved. This process provides a concise and environmentally sustainable access to a series of oxindoles and dihydroquinolinones.

Photocatalytic Proton-Coupled Electron Transfer Enabled Radical Cyclization for Isoquinoline-1,3-diones Synthesis

“…Despite significant progress in radical addition-induced cyclization for this transformation, the exploration and development of a photocatalytic single electron reduction mode for the reductive cyclization of acrylamide derivatives remain elusive and little explored due to the low electrophilicity of α,β-unsaturated amides . To overcome this challenge, Chen and co-workers recently reported a photocatalytic charge-transfer complex that enables single electron reduction of α,β-unsaturated amides, serving as a key step for the reductive cyclization of acrylamides using thiolate as a catalytic electron donor (Scheme c) .…”

Synthesis Enabled by E-to-Z Isomerization Using CBZ6 as Energy Transfer Photocatalyst

“…An efficient visible-light photocatalyst for E → Z -isomerization is the key for the aforementioned transformations via Z -isomers. In this work, we wish to report our exploration of photocatalytic E → Z -isomerization promoted by an organic photoreductant CBZ6 as a photocatalyst. − The E → Z -isomerization enables the synthesis of corresponding targets via Z -isomers (Scheme b).…”

Photocatalytic Redox-Neutral Alkoxyacylation of Alkenes

“…CBZ6 is known as a redox-neutral non-donor–acceptor type of organo photocatalyst. − It has demonstrated a strong reductive potential [−2.16 V vs the saturated calomel electrode (SCE)], which results from the twisted carbazole core, and therefore enables a series of unconventional redox transformations, such as the umpolung β-oxygenation of α,β-acrylamides . In this process, CBZ6 participated in the oxidation of an α-carbonyl radical to the cationic intermediate and therefore enabled the reversed regioselectivity.…”