Ligand electronic fine-tuning and its repercussion on the photocatalytic activity and mechanistic pathways of the copper-photocatalysed aza-Henry reaction

Abstract

A family of six structurally related heteroleptic copper(I) complexes of the form of [Cu(N^N)(P^P)]+ bearing a 2,9-dimethyl-1,10-phenanthroline diimine (N^N) ligand and a series of electronically tunable xantphos (P^P) ligands have...

Fluorescent Hybrid Porous Polymers as Sustainable Heterogeneous Photocatalysts for Cross-Dehydrogenative Coupling Reactions

“…Importantly, in the course of our experiments, the reactive superoxol radical anion (O 2 •– ) was never detected in the solution. , Reaction between radical A and HOO • result in the formation of the iminium ion C via two possible pathways: radical cross-coupling to produce the hydroperoxide intermediate B , which could undergo protonation to produce C with concomitant formation of H 2 O 2 , or by one-electron oxidation to form HOO – and C . Ultimately, the highly nucleophilic iminium C can be easily trapped by nitromethane to yield the expected product 3a . , …”

“…Thus, to “capture” visible photons and efficiently convey their energy into the reaction flask, it is necessary to use an adequate photocatalyst or photosensitizer. − In this context, complexes based on ruthenium­(II) and iridium­(III) are among the most popular photocatalysts, including strong photooxidants and strong photoreductants . Recently, eco-friendly copper­(I) complexes have gained momentum due to their, in many cases, superior photoredox properties. , These have been successfully used in diverse applications including proton reduction, cyclizations, C–H derivatization reactions, and atom-transfer radical additions (ATRAs). − Despite the broad success of transition-metal-based photocatalysts and photosensitizers, most of them suffer from major disadvantages like high costs, toxicity, poor stability, and low recyclability.…”

Cross‐dehydrogenative Coupling of N‐Aryl Tetrahydroisoquinolines Catalyzed by an Anthraquinone‐containing Polymeric Photosensitizer

“…radical and intermediate 9 [2c] . Next, the newly formed intermediates 8 and 9 couple with each other to produce hydroperoxide intermediate 10 , which further undergoes protonation to generate imine ion 11 and H 2 O 2 [32d] . Alternatively, the SET process may also occur between 9 and AQ * ‐PHEMA to afford cation 11 [32b,2c] .…”

“…It should not be ruled out that, the photocatalyzed coupling between THIQ and nitromethane may also proceed through oxygen photosensitization followed by SET between the resulting singlet oxygen and the amine substrate. Thus, in this case, AQ*‐PHEMA may generate singlet oxygen ( 1 O 2 ) with triplet oxygen ( 3 O 2 ), and then reacts with 1 a through a SET process to afford radical cation 8 (Figure 9, Path B) [32c,d] …”

Phenazine Radical Cations as Efficient Homogeneous and Heterogeneous Catalysts for the Cross‐Dehydrogenative Aza‐Henry Reaction

“…This reaction has been widely used in organic synthesis since the introduced nitro synthon can be converted into 1,2‐diamines [76,77] or α‐aminocarbonyls ( Nef reaction) [78] . There are many catalytic approaches to achieve this transformation, mostly using noble metals like Ru, [79] and Ir, [80] and more recently under photochemical conditions using metal complexes [81,82] . Metal‐free photocatalytic systems, which often use Eosin as photosensitizer, [83] are relatively rare [84] .…”