Rational Design of Highly Phosphorescent Nanoclusters for Efficient Photocatalytic Oxidation

Analyzing the molecular structure-photophysical property correlations of metal nanoclusters to accomplish function-oriented photocatalysis could be challenging. Here, the selective heteroatom alloying has been exploited to a Au15 nanocluster, making up a structure-correlated nanocluster series, including homogold Au15, bimetallic AgxAu15-x and CuxAu15-x, trimetallic AgxCuyAu15-x-y, and tetrametallic Pt1AgxCuyAu15-x-y. Their structure-dependent photophysical properties were investigated due to the atomically precise structures of these nanoclusters. Cu-alloyed CuxAu15-x showed intense phosphorescence and the highest singlet oxygen production efficiency. Moreover, the generation of 1O2 species from excited nanoclusters enabled CuxAu15-x as a suitable catalyst for efficient photocatalytic oxidation of silyl enol ethers to produce α,β-unsaturated carbonyl compounds. The generality and applicability of the CuxAu15-x catalysts toward different photocatalytic oxidations were assessed. Overall, this study presents an intriguing Au15-based cluster series enabling an atomic-level understanding of structure-photophysical property correlations, which hopefully provides guidance for the fabrication of cluster-based catalysts with customized photocatalytic performance.

Photochemical Desaturation and Epoxidation with Oxygen by Sequential Flavin Catalysis

Catalytic desaturations are important strategies for the functionalization of organic molecules. In nature, flavoenzymes mediate the formation of α,β-unsaturated carbonyl compounds by concomitant cofactor reduction. Contrary to many laboratory methods for these reactions, such as the Saegusa-Ito oxidation, no transition metal reagents or catalysts are required. However, a molecular flavin-mediated variant has not been reported so far. We disclose a photochemical approach for silyl enol ether oxidation, which leads to α,β-unsaturated ketones (13 examples) in very good yields. The flavin catalysts are stable throughout the desaturation reaction, and we successfully applied them in a subsequent aerobic epoxidation by simply changing the reaction conditions. This protocol allowed us to directly convert silyl enol ethers into α,β-epoxyketones in a one-pot fashion (12 examples). Sequential flavin catalysis is not limited to one specific reactivity combination and can, inter alia, couple the photochemical oxidation with radical additions. We anticipate that flavin-catalyzed desaturation will be applicable to other substrate classes and that its sequential catalytic activity will enable rapid substrate diversification.

[Ru(NꓥNꓥN)2-Ce]-based Framework for Photocatalytic Sulfide Oxidation and Hydrogen Production

Using photosensitized Ru(NꓥNꓥN)2-metalloligand, a series of Ce-frameworks were synthesized. The incorporation of visible-light-responsive Ru(NꓥNꓥN)2-unit endows the Ce-frameworks with photocatalytic activities in both sulfide oxidation and hydrogen production. The doping of...

Recent Progress in Organophotoredox Reaction

In the past decade, visible light photoredox catalysis has been established as a gentle and powerful strategy for the activation of organic molecules. As an important part of it, organic...

Scalable Birch reduction with lithium and ethylenediamine in tetrahydrofuran

[Figure: see text].

A Synthetic Route to The Core Structure of (-)-Retigeranic Acid A

Retigeranic acid A is a uniquely structured pentacyclic sesterterpene bearing eight stereogenic centers. We report a concise route to the core structure of (-)-retigeranic acid A. The stereochemistry of its six chiral centers and three quaternary carbon centers was well-controlled. This route features two intramolecular Pauson-Khand reactions (IMPKRs): the first forged the D and E rings to deliver the triquinane subunit, and the second constructed the A and B rings and diastereoselectively installed the quaternary C_6a center.

Visible-light-promoted oxidation/condensation of benzyl alcohols with dialkylacetamides to cinnamides

An oxidative cross-coupling reaction of benzyl alcohols with dialkylacetamides was developed to construct cinnamides under visible-light-enabled photocatalytic conditions.

Visible-Light-Induced Organic Photochemical Reactions through Energy-Transfer Pathways

Visible-light photocatalysis is a rapidly developing and powerful strategy to initiate organic transformations, as it closely adheres to the tenants of green and sustainable chemistry. Generally, most visible-light-induced photochemical reactions occur through single-electron transfer (SET) pathways. Recently, visible-light-induced energy-transfer (EnT) reactions have received considerable attentions from the synthetic community as this strategy provides a distinct reaction pathway, and remarkable achievements have been made in this field. In this Review, we highlight the most recent advances in visible-light-induced EnT reactions.

Organocatalysis: A Brief Overview on Its Evolution and Applications

The use of small organic molecules as catalysts has gained increasing importance recently. These substances, the so-called organocatalysts, present a lot of advantages, like being less toxic, less polluting, and more economically viable than the organometallic catalysts that dominate asymmetric synthesis. This work intends to briefly show some classic works and recent publications, explaining the advantages of organocatalysis and the different types of compounds used in this field, as well as their course of action.

Thiol-ene/oxidation tandem reaction under visible light photocatalysis: synthesis of alkyl sulfoxides

The photocatalyzed synthesis of sulfoxides from alkenes and thiols has been carried out using Eosin Y.

The photocatalyzed synthesis of sulfoxides from alkenes and thiols has been carried out using Eosin Y. This is a metal-free method which uses a low catalyst loading, atmospheric oxygen as the oxidant, and visible light conditions (green light). A mechanism has been proposed that is consistent with the experimental results.

Photocatalysis in organic and polymer synthesis

This review, with over 600 references, summarizes the recent applications of photoredox catalysis for organic transformation and polymer synthesis. Photoredox catalysts are metallo- or organo-compounds capable of absorbing visible light, resulting in an excited state species. This excited state species can donate or accept an electron from other substrates to mediate redox reactions at ambient temperature with high atom efficiency. These catalysts have been successfully implemented for the discovery of novel organic reactions and synthesis of added-value chemicals with an excellent control of selectivity and stereo-regularity. More recently, such catalysts have been implemented by polymer chemists to post-modify polymers in high yields, as well as to effectively catalyze reversible deactivation radical polymerizations and living polymerizations. These catalysts create new approaches for advanced organic transformation and polymer synthesis. The objective of this review is to give an overview of this emerging field to organic and polymer chemists as well as materials scientists.

Eosin Y–Yb(OTf)3 catalyzed visible light mediated electrocyclization/indole ring opening towards the synthesis of heterobiaryl-pyrazolo[3,4-b]pyridines

Synthesis of heterobiaryl-pyrazolo[3,4-b]pyridines via Lewis acid and visible light photo-catalysis at room temperature.

Total synthesis of orientalol F via gold-catalyzed cycloisomerization of alkynediol

The total synthesis of orientalol F was accomplished in 13 steps using gold-catalyzed tandem cycloisomerization of alkynediol as a key step.

Eosin Y catalysed photoredox synthesis: a review

In recent years, photoredox catalysis using eosin Y has come to the fore front in organic chemistry as a powerful strategy for the activation of small molecules.

Carboxylation of styrenes with CBr4and DMSO via cooperative photoredox and cobalt catalysis

Cooperative photoredox and cobalt catalyzed carboxylation of styrenes with CBr₄to afford the corresponding α,β-unsaturated carboxylic acids has been realized through radical addition and Kornblum (DMSO) oxidation.

Synthesis of 1,4-Dicarbonyl Compounds from Silyl Enol Ethers and Bromocarbonyls, Catalyzed by an Organic Dye under Visible-Light Irradiation with Perfect Selectivity for the Halide Moiety over the Carbonyl Group

We report the visible-light-induced radical coupling reaction of silyl enol ethers with α-bromocarbonyl compounds to give 1,4-dicarbonyls. The reaction was effectively accelerated using an inexpensive organic dye (eosin Y) as a photoredox catalyst. 1,4-Dicarbonyl compounds alone were afforded, without the generation of carbonyl adducts of the α-halocarbonyls, which are usually generated in the presence of fluoride anions or Lewis acids. A variety of silyl enol ethers, α-bromoketones, α-bromoesters, and α-bromoamides were applied to this system to produce the coupling compounds.

Visible-Light-Enabled Decarboxylative Sulfonylation of Cinnamic Acids with Sulfonylhydrazides under Transition-Metal-Free Conditions

Decarboxylative cross-coupling reactions of cinnamic acids with sulfonylhydrazides were explored using oxygen as the sole terminal oxidant, realizing a conceptually novel technology for vinyl sulfone synthesis under the synergistic interactions of visible light irradiation, organic dye-type photocatalyst eosin Y, KI, and Cs2CO3 at room temperature.

Oxidative organophotoredox catalysis: a regioselective synthesis of 2-nitro substituted imidazopyridines and 3-substituted indoles, initiated by visible light

Intramolecular C–N heterocyclization and C–C bond formation under visible light irradiation at room temperature was accomplished with a metal-free photoredox catalyst.

Visible light-mediated decarboxylative amination of indoline-2-carboxylic acids catalyzed by Rose Bengal

A visible-light-induced decarboxylative amination of N-protected indoline-2-carboxylic acids and azodicarboxylate esters catalyzed by Rose Bengal has been developed.

A family of low molecular-weight, organic catalysts for reductive C-C bond formation

Hydrazines form a new family of low molecular-weight reducing agents for diazonium salts. Using only small amounts of hydrazine catalyst, the coupling of diazonium salts to a variety of reactive partners has been achieved, without the requirement for either metal adjuvants or irradiation with visible or ultraviolet light. The generality of the concept proposed herein as well as its advantages in the preparative scale is outlined and discussed.

Synthetic applications of eosin Y in photoredox catalysis

Eosin Y, a long known dye molecule, has recently been widely applied as a photoredox catalyst in organic synthesis. Low cost and good availability make eosin Y an attractive alternative to typical inorganic transition metal photocatalysts. We summarize the key photophysical properties of the dye and the recent synthetic applications in photoredox catalysis.

Synthesis of cross-linked polymers via multi-component Passerini reaction and their application as efficient photocatalysts

Cross-linked polymers containing Ru complexes synthesized via multi-component Passerini reaction were shown to be highly effective and recyclable heterogeneous photocatalysts.