A copper-catalyzed intramolecular cascade carbocyclization/1,2-migration of C-2 indolyl-allenol has been achieved to construct the library of 2-sulfonyl carbazoles, which possess considerable biological significance. This modular protocol is operationally simple, exhibiting a broad substrate scope with consistently high yields. Additionally, gram-scale synthesis, product diversification of 2-sulfonyl carbazoles, and DFT studies of the catalytic cycle have been performed. Overall, this study unfolds a new strategy for the one-pot synthesis of sulfonyl carbazoles, which holds significance in medicinal and material chemistry.

Dearomative cycloaddition reactions of indoles offer a powerful strategy for rapidly increasing molecular complexity, yet intermolecular variants that proceed with high regio- and diastereocontrol remain uncommon. Herein, we report an iron(iii) chloride-mediated dearomative formal [3 + 2] cycloaddition of indoles with arylsulfonyl allenols, providing direct access to densely functionalized cyclopenta[b]indoles with excellent diastereoselectivity. The reaction proceeds under mild Lewis acidic conditions without the use of precious metal catalysts and displays broad substrate scope, tolerating diverse substitution patterns on the indole core and allenols, including electron-rich, electron-deficient, sterically hindered, and fused systems, affording the desired tricyclic scaffold in moderate to excellent yields. The synthetic utility of this protocol is demonstrated through late-stage functionalization of pharmaceutically relevant indole-containing molecules, double cascade dearomative cycloaddition, gram-scale synthesis, and downstream product diversification. Mechanistic studies, including DFT energy calculations and isotopic labeling experiments, support an ionic, non-radical pathway involving Lewis acid activation of the allenol to generate a transient electrophilic intermediate, followed by dearomative cyclization. This operationally simple and sustainable method enables rapid construction of structurally complex, nonplanar cyclopenta[b]indole frameworks of potential relevance in medicinal chemistry.

In recent decades, there has been a notable increase in interest surrounding the direct functionalization of carbonyl compounds, attributed to their extensive applications across various fields. However, conventional methodologies have predominantly relied on stoichiometric amounts of expensive and often environmentally detrimental metal oxidants, which present significant sustainability challenges in the arylation processes. In contrast to traditional transition metal-catalysed arylations, photochemical methods offer environmentally friendly reaction profiles, greater operational simplicity, and access to novel reactivity modes that are not achievable under thermal conditions. This review highlights recent advancements in visible-light-driven arylation techniques that enable the formation of carbon-carbon (C-C) bonds at either the α- or the β-position, or directly at the carbonyl center of carbonyl compounds. The tutorial review also emphasizes the mechanistic insights, including radical chain propagation, proton-coupled electron transfer (PCET), and energy transfer pathways, that underpin these transformations. By leveraging the potential of photocatalysis, particularly through single-electron transfer (SET) processes and radical-mediated mechanisms, these transformations demonstrate remarkable tolerance for a variety of functional groups and regioselectivity, even within challenging molecular structures by utilizing diverse arylating sources (including aryl diazonium salts, aryl halides, and cyanoarenes). The aim is to provide a concise overview of current methodologies, mechanistic insights, and future directions in photochemical arylation of carbonyl compounds, emphasizing its advancements toward sustainability in modern synthetic organic chemistry.

Abstract Asymmetric catalysis stands at the forefront of modern chemistry, serving as a cornerstone for the efficient synthesis of enantiopure chiral molecules, known for their high selectivity. In recent years, merging electrocatalysis and photocatalysis into a hybrid method called electrophotoredox catalysis has become the focus of extensive research in organic synthesis, providing powerful and complementary strategies for constructing complex molecular architectures. This short review highlights recent advances on an emerging topic, photoelectrochemical asymmetric catalysis (PEAC), which shows potential for the efficient and sustainable production of enantiomerically enriched compounds by harnessing electron and photon in one pot. This approach facilitates efficient and sustainable redox processes for the formation of an asymmetric center through C–H functionalization, decarboxylative functionalization, dehydrogenative cycloaddition reaction, cross-coupling, and difunctionalization of olefins.

The judicious incorporation of main group elements such as boron-nitrogen Lewis pair motifs into π-conjugated frameworks has emerged as a powerful strategy for developing novel functional hybrid materials with significant potential for application in biological and materials chemistry. Herein, we report the concise synthesis and comprehensive photophysical characterization of a boron-nitrogen fused [7]helicene, which shows emission in the yellow-green region, prolonged fluorescence lifetimes, and redox activity. Single-crystal X-ray diffraction studies confirm the coexistence of P- and M-helical enantiomers, which adopt an ordered heterochiral packing arrangement in the solid state. Furthermore, the helical boron-nitrogen adduct was investigated in cell imaging studies, where it exhibits enhanced intracellular photostability, lower cytotoxicity, and effective staining of cytoplasmic compartments. Additionally, to gain insight into its electronic structure and frontier molecular orbital energetics, density functional theory (DFT) calculations were performed.

Propargylamines constitute a valuable class of α-alkynyl amines that are widely encountered in medicinal chemistry and chemical biology. Herein, we report a regiospecific α-C(sp3)–H alkynylation of tertiary amines that enables the direct synthesis of propargylamines from unactivated tertiary amines and terminal alkynes. The transformation proceeds under mild, base-free conditions using sustainable low-energy photon irradiation and is initiated by single-electron-transfer (SET) activation of the tertiary amine, generating a reactive iminium intermediate that undergoes nucleophilic coupling with a transient Cu(I)–acetylide species. The protocol accommodates a diverse range of tertiary amines and terminal alkynes, including bioactive molecules and pharmaceuticals, providing access to structurally diverse internal alkynes and versatile click-ready terminal alkynes with excellent functional-group tolerance. The synthetic utility of the method is further demonstrated through gramscale reactions, while comprehensive mechanistic investigations provide insights into the photoredox and copper catalytic pathways underlying this transformation.

Introducing the amine functionality to readily available feedstock chemicals is an effective strategy to rapidly enhance the molecular complexity and access valuable scaffolds. Herein, we have developed a red photon-driven N-aminomethylation of indoles utilizing a (n)PrDMQA(+) organic photocatalyst. Under red-photon irradiation, amine radical cations exclusively generate less hindered iminium species, which are then sequentially converted into sterically crowded tertiary amines of interest in organic synthesis, enabling a high-yield N-C(sp(3)) coupling reaction under mild conditions. This protocol demonstrates a broad substrate scope, allowing late-stage modification of bioactive natural compounds and pharmaceuticals under mild conditions. Control experiments and DFT studies on transient intermediates confirmed the mechanistic pathway, highlighting the generation of a kinetically favored iminium ion to generate a library of aminated indole derivatives.

Herein, we present a two-step protocol for the synthesis of an organo-fluorophore using palladium-catalyzed carbo-oxygenative cyclization of chloroprene derivatives. Protocol is well-tolerated with a broad substrate scope and is feasible at gram-scale synthesis. Mechanistic studies were conducted using H2O18 labeling and density functional theory (DFT) analysis. Notably, organofluorophores show strong photoluminescence and fluorescence lifetimes along with notable redox potential. Furthermore, cell viability studies showed low toxicity and high selectivity for lysosomes, making them promising candidates for green lysotracker imaging agents.

A ruthenium-catalyzed intramolecular cascade cyclization of allene-alkyne has been achieved. This method offers a streamlined and atom-economical approach for the construction of sulfone bearing 1H-cyclopenta[a]naphthalenes, an important structural scaffold that exists in biologically active compounds. Our approach, backed by mechanistic insights from deuterium labeling, DFT calculations, and potential for reaction scale-up, presents synthetic chemists with an invaluable tool for efficiently producing a distinct carbon framework in a one-pot manner. This protocol is operationally simple, exhibiting a broad substrate scope with consistently high yields.

We report a palladium-catalyzed sequential oxycyclization of indole-tethered allene to construct oxepino indole cores with yields up to 91%. This method showcases the C2 umpolung activation of indoles via η3-π-allyl reactivity and enables efficient synthesis without side products. Furthermore, extensive mechanistic investigations, encompassing control experiments, X-ray crystallographic studies, and DFT analysis, have been conducted to elucidate the underlying mechanisms. Additionally, gram-scale synthesis and product diversification have been performed to illustrate the synthetic utility of this transformation.

Polyaromatic quaternary ammonium salts (PQASs) are of significant interest due to their promising applications in biological and materials sciences. The incorporation of a heteroatom significantly modifies the electronic and chemical properties of these molecules, influencing their absorption and emission characteristics, as well as the HOMO-LUMO gap. Herein, we report the synthesis and photophysical investigation of [7]helicene-backboned quaternary ammonium salts. These compounds exhibit excellent stability, absorb light in the visible region with λabs ranging from 385 to 395 nm, and show emission in the green wavelength spectrum at λem between 541 and 552 nm. Also, they are redox-active and feature a structurally defined double helical axis. Single-crystal X-ray diffractometry has demonstrated the presence of a double helical structure within the crystal packing, which is characterized by the linkage of M-P and P-M heterodimers. Additionally, they show photoluminescence capability (ϕf) of up to 0.57, with fluorescence lifetimes in the range of 1.81-3.17 ns. Notably, these fluorophores turned out to be potential cell imaging agents. Colocalization studies that utilized LysoTracker Red probes as standard lysosomal trackers demonstrated that the [7]helicene QAS probe is efficacious in specifically labeling lysosomes in the neuroblastoma (N2a) cell line and RAW 264.7 macrophage cells. Additionally, to elucidate their electronic profiles, we employed time-dependent density functional theory calculations.

Diffusion-limited kinetics is a key mechanistic debate when consecutive photoelectron transfer (conPET) is discussed in photoredox catalysis. In situ generated organic photoactive radicals can access catalytic systems as reducing as alkaline metals that can activate remarkably stable bonds. However, in many cases, the extremely short-lived transient nature of these doublet state open-shell species has led to debatable mechanistic studies, hindering adoption and development. Herein, we document the use of an isolated and stable neutral organic nPrDMQA radical as a highly photoreducing species. The isolated radical offers a unique platform to investigate the mechanism behind the photocatalytic activity of organic photocatalyst radicals. The involvement of reduced solvent is observed, formed by single electron transfer (SET) between the short-lived excited state nPrDMQA radical and the solvent. In our detailed mechanistic studies, spectroscopic and chemical affirmation of solvent reduction is strongly evident. Reduction of aryl halides, including difluoroarenes is presented as a model study of the conPET method. Further, the activation of N2O, a greenhouse gas that is yet to be activated by photoredox catalysis, is showcased in the absence of a transition metal.

A red-light (λ = 640 nm)-mediated C-3 formylation of indoles utilizing a helical carbenium ion as a photocatalyst and 2,2-dimethoxy-N,N-dimethylethanamine as a formylating source is presented.

Open shell species are alluring significant attention owing to their unique physiochemical properties in redox chemistry for activating remarkably stable bonds. Solvated electrons are one of them that have been extensively investigated due to their high reduction potential (Ered=-2.9 V vs SHE in CH3CN), diverse substrate activation, and promising applications. If the activating species have a larger redox potential with a longer lifetime, then the broader range of substrates will be activated. Hence, the solvated electron qualifies as a super-reductant with these qualities. However, due to safety issues, generating solvated electrons by dissolving alkali metals in an ammoniated solvent limits its use towards complicated organic transformations. Instead photochemically generated solvated electron overcome this limitation and is identified as a user-friendly, sustainable, and much safer alternative approach for producing solvated electrons. In this minireview, we have comprehensively highlighted the recent key methods to generate the solvated electron photochemically, characterization techniques, and its application in organic transformations with selected examples. The minireview provides new opportunities for chemists to understand the conceptual, physical, and mechanistic chemistry principle of this super reductant for exploiting a new photochemical route for the transformations that are difficult to achieve by other means. image

Organosilanes have secured a special place in the synthetic world for several decades. However, among them, allylsilanes are a choice reagent for organic chemists to develop novel organic transformations. In recent years researchers have proved that visible-light photoredox catalysis has emerged as one of the most mild, sustainable, straightforward, and efficient strategies to construct simple to complex molecules with or without enantioselectivity. This review provides an in-depth analysis of recent advances and strategies employed in visible-light photoredox catalysis for allylsilane and its analogues for the development of various organic transformations. The review is divided into sections, each focused on a specific reactivity of allylsilane under light irradiation with C(sp2) center arene or alkene, C(sp2) center carbonyl, and C(sp3) center carbon functionality. In this review, we present optimization data, reaction scope, and mechanistic aspects to bring forward specific reactivity and selectivity trends of allylsilane in photoredox conditions.

Chromoselective bond activation has been achieved in organic helicenium (nPr-DMQA+)-based photoredox catalysis. Consequently, control over chromoselective C(sp2)-X bond activation in multihalogenated aromatics has been demonstrated. nPr-DMQA+ can only initiate the halogen atom transfer (XAT) pathway under red light irradiation to activate low-energy-accessible C(sp2)-I bonds. In contrast, blue light irradiation initiates consecutive photoinduced electron transfer (conPET) to activate more challenging C(sp2)-Br bonds. Comparative reaction outcomes have been demonstrated in the α-arylation of cyclic ketones with red and blue lights. Furthermore, red-light-mediated selective C(sp2)-I bonds have been activated in iodobromoarenes to keep the bromo functional handle untouched. Finally, the strength of the chromoselective catalysis has been highlighted with two-fold functionalization using both photo-to-transition metal and photo-to-photocatalyzed transformations.

Building blocks with low connectivity and no embedded directionality are prone to polymorphism, as demonstrated by the diversity of 4-connected zeolitic nets (>250). As a result, their deployment for design in reticular and isoreticular chemistries remains a challenge. However, the ability to control geometrical peculiarities offers potential to deviate from the assembly of default structures. Here we report the face-directed assembly of >20 isoreticular zeolite-like metal–organic frameworks (ZMOFs) by using polytopic expanding and tightening centring structure-directing agents (cSDAs). The cSDAs are selected with the appropriate geometrical coding information to alter and control the orientation of adjacent supermolecular building blocks. The ZMOFs have an underlying sodalite ( sod ) topology that is remarkably suited for the rational assembly of multinary materials. In addition to a variety of metal cations (In, Fe, Co and Ni), a diverse range of cSDAs (di-, tri-, tetra-, hexa-, pyridyl or imidazole) are used and combined. Our approach enables isoreticular possibilities at both extremities of the porous materials spectrum: In- sod -ZMOF-102 exhibits small pore aperture suitable for efficient separation, while Fe- sod -ZMOF-320 with 48-Å-wide mesopores exhibits high hydrogen uptake, methane storage working capacity and a high gravimetric working capacity for oxygen.

Over the past several decades, there has been a surge of interest in harnessing the functionalization of C(sp3)-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(sp3)-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(sp3)-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(sp3)-H bond functionalization through organic electro-photochemistry.