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Many photocatalysts were initially developed or used as emitters for organic light emitting diodes (OLEDs). This feature article summarizes the different generations of OLED emitters and connects the photophysical processes with those relevant for photocatalysis. The focus is on the general properties OLED emitters and photocatalysts are designed for and how photocatalysis has benefitted from OLED research. Sometimes optimization of an OLED emitter leads to a better photocatalyst while some properties are optimized into opposite directions. To discover new classes of photocatalysts in the future it is important to consider what good OLED emitters and good photocatalyst have in common and where they diverge. Within recent years, fully organic thermally activated delayed fluorescence (TADF) emitters had the most significant impact in both fields and thus are discussed with specific focus. [ABSTRACT FROM AUTHOR]

Tandem processes are valuable tools that allow to build molecular complexity while reducing waste production and the number of steps of synthetic routes. In this work, the in situ photooxidation of benzyl alcohols to the corresponding benzaldehydes is coupled with a Knoevenagel condensation for the preparation of benzylidenemalononitrile derivatives. In this rapid one‐pot tandem process, sodium anthraquinone‐1,5‐disulfonate (SAS) and β‐alanine are employed as safe and inexpensive catalysts, while air is used as a terminal oxidant. Moreover, using water as reaction medium results in most cases in the precipitation of the target products, thus facilitating their isolation. [ABSTRACT FROM AUTHOR]

Isotonitazene belongs to a potent class of μ‐opioid receptor (μOR) ligands, known as nitazenes. The lack of knowledge surrounding this agonist and others in its class has sparked thorough re‐investigations. To aid in these investigations, the purportedly covalent yet underexplored nitazene BIT was biochemically re‐evaluated in this work, along with a newly synthesized analogue, Iso‐BIT. Moreover, in the pursuit of understanding the mechanism, function and interactions of the μOR, this study involved developing photoswitchable nitazene derivatives as potential probe molecules. Converting known ligands into azo‐containing photoswitchable derivatives offers the opportunity to modulate ligand structure with light, allowing for photocontrol of compound activity. While photocontrol of μOR activity could not be entirely achieved, photophysical evaluation of these 2‐benzimidazole azo‐arenes revealed a novel photoswitch scaffold that responds to visible light. Furthermore, azo‐containing 2 e and 3 e emerged as promising nitazene derivatives that were able to form an exceptionally high fraction of covalent‐ligand receptor complexes with wild‐type μOR at physiological pH. [ABSTRACT FROM AUTHOR]

This article explores a new method for the dichlorination of alkenes using iron complexes as catalysts. The authors describe a photocatalytic process that utilizes iron chloride and light-induced ligand-to-metal-charge transfer to generate reactive chlorine radicals. The reaction is efficient and selective, producing 1,2-dichloride compounds that are valuable intermediates in organic synthesis. The article also investigates the mechanism of the reaction and examines the range of substrates that can be used in this iron-catalyzed photodichlorination process. [Extracted from the article]

Cross-coupling reactions play a vital role in modern organic synthesis, enabling the construction of necessary C–C or C–(het)atom bonds for synthetic transformations. Although C(sp2)–C and C(sp2)–N cross-coupling reactions have received significant attention, recent advancements have also highlighted the significance of C(sp2)–S cross-coupling reactions. These reactions lead to the synthesis of valuable compounds, including pharmaceuticals and materials. In a recent report, we introduced Adaptive Dynamic Homogeneous Catalysis (AD-HoC) as an efficient method for C(sp2)–S cross-coupling reactions. This method operates without the need for any ligands, base, or additional additives, relying solely on essential parameters. In this report, we discuss the use of mesoporous graphitic carbon nitride (mpg-CN) as an all-organic heterogeneous photocatalyst in such transformations. The versatility and robustness of the reaction are showcased with fifty synthetic examples, achieving up to a 98% yield. The use of mpg-CN as a catalyst additionally enables the easy recovery of the photocatalyst from the reaction mixture and facilitates the sequential execution of multiple cross-coupling reactions with consistent yields of the desired products using a simple setup. This approach is a significant advancement in the field, both in terms of operational simplicity and environmental impact, traits that we all envision for sustainability. [ABSTRACT FROM AUTHOR]

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Photocatalytic reactions involving a reductive radical‐polar crossover (RRPCO) generate intermediates with carbanionic reactivity. Many of these proposed intermediates resemble highly reactive organometallic compounds. However, conditions of their formation are generally not tolerated by their isolated organometallic versions and often a different reactivity is observed. Our investigations on their nature and reactivity under commonly used photocatalytic conditions demonstrate that these intermediates are indeed best described as free, superbasic carbanions capable of deprotonating common polar solvents usually assumed to be inert such as acetonitrile, dimethylformamide, and dimethylsulfoxide. Their basicity not only towards solvents but also towards electrophiles, such as aldehydes, ketones, and esters, is comparable to the reactivity of isolated carbanions in the gas‐phase. Previously unsuccessful transformations thought to result from a lack of reactivity are explained by their high reactivity towards the solvent and weakly acidic protons of reaction partners. An intuitive explanation for the mode of action of photocatalytically generated carbanions is provided, which enables methods to verify reaction mechanisms proposed to involve an RRPCO step and to identify the reasons for the limitations of current methods. [ABSTRACT FROM AUTHOR]

A convenient and versatile approach to important 1‐azaspirocyclic systems relevant to medicinal chemistry and natural products is reported herein. The main strategy relies on a reductive decarboxylative cyclization of redox‐active esters which can be rapidly assembled from abundant cyclic azaacids and tailored acceptor sidechains, with a focus on alkyne acceptors enabling the generation of useful exo‐alkene moieties. Diastereoconvergent variants were studied and could be achieved either through remote stereocontrol or conformational restriction in bicyclic carbamate substrates. Two sets of metal‐free photocatalytic conditions employing inexpensive eosin Y were disclosed and studied experimentally to highlight key mechanistic divergences. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride has attracted significant interest in heterogeneous photocatalysis due to its activity under visible‐light irradiation. Herein, we report on using carbon nitride‐coated NMR tubes for in situ studies of photocatalytic reaction mechanisms. In a first step, we exploited carbon nitride‐coated crimp vials as batch photoreactors for visible photocatalytic fluorinations of unactivated C(sp3)−H bonds, with moderate to excellent yields and reusability over multiple cycles. Eventually, carbon nitride‐coated NMR tubes were used as a photoreactor by coupling them with optical fiber irradiation directly inside the spectrometer. This enabled us to follow the reaction with in situ NMR spectroscopy identifying reactive intermediates otherwise elusive in conventional analyses. The method provides advantages for the study of photocatalytic mechanisms of complex reactions and substantially reduces the need of comparative tests for depicting reaction intermediates and conversion pathways. [ABSTRACT FROM AUTHOR]

Gamma aminobutyric acid type A receptors (GABA A Rs) play a key role in the mammalian central nervous system (CNS) as drivers of neuroinhibitory circuits, which are commonly targeted for therapeutic purposes with potentiator drugs. However, due to their widespread expression and strong inhibitory action, systemic pharmaceutical potentiation of GABA A Rs inevitably causes adverse effects regardless of the drug selectivity. Therefore, therapeutic guidelines must often limit or exclude clinically available GABA A R potentiators, despite their high efficacy, good biodistribution, and favorable molecular properties. One solution to this problem is to use drugs with light-dependent activity (photopharmacology) in combination with on-demand, localized illumination. However, a suitable light-activated potentiator of GABA A Rs has been elusive so far for use in wildtype mammals. We have met this need by developing azocarnil, a diffusible GABAergic agonist-potentiator based on the anxiolytic drug abecarnil that is inactive in the dark and activated by visible violet light. Azocarnil can be rapidly deactivated with green light and by thermal relaxation in the dark. We demonstrate that it selectively inhibits neuronal currents in hippocampal neurons in vitro and in the dorsal horns of the spinal cord of mice, decreasing the mechanical sensitivity as a function of illumination without displaying systemic adverse effects. Azocarnil expands the in vivo photopharmacological toolkit with a novel chemical scaffold and achieves a milestone toward future phototherapeutic applications to safely treat muscle spasms, pain, anxiety, sleep disorders, and epilepsy.

Over the past several decades, there has been a surge of interest in harnessing the functionalization of C(sp 3 )-H bonds due to their promising applications across various domains. Yet, traditional methodologies have heavily leaned on stoichiometric quantities of costly and often environmentally harmful metal oxidants, posing sustainability challenges for C-H activation chemistry at large. In stark contrast, the emergence of electro-photocatalytic-driven C(sp 3 )-H bond activation presents a transformative alternative. This approach offers a viable route for forging carbon-carbon and carbon-heteroatom bonds. It stands out by directly engaging inert C(sp 3 )-H bonds, prevalent in organic compounds, without the necessity for prefunctionalization or harsh reaction conditions. Such methodology simplifies the synthesis of intricate organic compounds and facilitates the creation of novel chemical architectures with remarkable efficiency and precision. This review aims to shed light on the notable strides achieved in recent years in the realm of C(sp 3 )-H bond functionalization through organic electro-photochemistry., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Photocatalytic reactions involving a reductive radical-polar crossover (RRPCO) generate intermediates with carbanionic reactivity. Many of these proposed intermediates resemble highly reactive organometallic compounds. However, conditions of their formation are generally not tolerated by their isolated organometallic versions and often a different reactivity is observed. Our investigations on their nature and reactivity under commonly used photocatalytic conditions demonstrate that these intermediates are indeed best described as free, superbasic carbanions capable of deprotonating common polar solvents usually assumed to be inert such as acetonitrile, dimethylformamide, and dimethylsulfoxide. Their basicity not only towards solvents but also towards electrophiles, such as aldehydes, ketones, and esters, is comparable to the reactivity of isolated carbanions in the gas-phase. Previously unsuccessful transformations thought to result from a lack of reactivity are explained by their high reactivity towards the solvent and weakly acidic protons of reaction partners. An intuitive explanation for the mode of action of photocatalytically generated carbanions is provided, which enables methods to verify reaction mechanisms proposed to involve an RRPCO step and to identify the reasons for the limitations of current methods., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A convenient and versatile approach to important 1-azaspirocyclic systems relevant to medicinal chemistry and natural products is reported herein. The main strategy relies on a reductive decarboxylative cyclization of redox-active esters which can be rapidly assembled from abundant cyclic azaacids and tailored acceptor sidechains, with a focus on alkyne acceptors enabling the generation of useful exo-alkene moieties. Diastereoconvergent variants were studied and could be achieved either through remote stereocontrol or conformational restriction in bicyclic carbamate substrates. Two sets of metal-free photocatalytic conditions employing inexpensive eosin Y were disclosed and studied experimentally to highlight key mechanistic divergences., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)