Applications of Photoredox Catalysis for the Radical-Induced Cleavage of C–C Bonds

Abstract

Selective cleavage of C-C bonds forms one of the greatest challenges in current organic chemistry, due to the relative strength of these bonds. However, such transformations are an invaluable instrument to break down and construct new carbon-carbon bonds. To achieve this, photochemistry can be used as a valuable tool to generate radicals and induce the cleavage of these bonds. This review paints a picture of some of the most influential contributions in this field from the last decade.

Photocatalysis as an Effective Tool for Upcycling Polymers into Value‐Added Molecules

“…Although photocatalysis has experienced tremendous success in building up demanding chemical structures, [51] the reverse way of deconstructing organic molecules, in particular non-strained compounds, through CÀ C bond scission still offers ample opportunities for development. [52,53] Further progress in this area will have significant impact on photochemical recycling of polymers and provide the means to reach beyond the types of polymers that are discussed herein. This being said, the range of polymers that are susceptible to photocatalytic depolymerizations is yet to be expanded.…”

Simple Strategy for Benzo[g]chromene Synthesis via a Photochemical Intramolecular Cyclization Reaction

“…A stirred solution of pquinone 3 (20.0 mg, 68.2 μmol) in CH 2 Cl 2 (12.0 mL, 5.68 mmol/L) was exposed to 18 W fluorescent light at ambient temperature for 2 h. 13 The reaction mixture was concentrated in vacuo, followed by SiO 2 flash column chromatography (CH 2 Cl 2 −n-hexane, 1:1) to obtain 2a (5.0 mg, 37%) as a yellow solid. IR 2-(Allyloxy)-3-chloronaphthalene-1,4-dione (6). The same procedure for the synthesis of 3 was used (1 h).…”

Photoredox Cleavage of a Csp3–Csp3 Bond in Aromatic Hydrocarbons

“…Photoredox catalysis has emerged as a powerful strategy for breaking inert bonds via radical mechanisms . This approach allows for the cleavage of unstrained acyclic C sp3 –C sp3 bonds under mild LED irradiation, , typically by single electron transfer to/from a redox-active group to generate transient oxygen or nitrogen radicals that undergo rapid β-scission. − However, despite recent advances, the selective cleavage of inert C sp3 –C sp3 bonds in hydrocarbons under mild conditions remains rare. In many cases, having ring tension is a prerequisite for the cleavage of these bonds, necessitating substrates with a specific level of molecular strain or tension.…”