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The prominence of saturated N -heterocycle motifs in pharmaceuticals is undeniable. Challenges associated with the alkylation of saturated N -heterocycle scaffolds to efficiently access new drug analogues are hampered by synthetically laborious routes. Stereocontrolled alkyl-substitutions onto saturated N -heterocycles are particularly difficult to access in high yields by traditional synthetic methods. Alternatively, C–H bond functionalization provides a new and powerful synthetic avenue by directly and selectively functionalizing/alkylating/ arylating the abundantly available C–H bonds of saturated N -heterocycles. This review highlights complementary methods for directly activating and functionalizing C–H bonds of saturated N -heterocycles chemo-, regio-, and or stereoselectively to access alkylated products. This synthetic challenge has required catalyst development to access useful N -heterocyclic building blocks or for late-stage functionalization. Early transition metal, late transition metal, photoredox, and electrochemical methods are discussed. The selective functionalization of α, β, and γ C–H bonds to form new C–C, C–N, C–O, and C–B bonds is presented. 1 Introduction 2 Early Transition Metal Catalyzed α-Alkylation 3 Late Transition Metal Catalyzed α-Functionalization 4 Photoredox-Catalyzed α-Functionalization 5 Electrochemical α-Functionalization 6 C–H Functionalization of β and γ C–H Bonds 7 Conclusions/Outlook [ABSTRACT FROM AUTHOR]

The trifluoromethylthio (SCF 3) and trifluoromethylselanyl (SeCF 3) groups possess high electron-withdrawing ability, excellent lipophilicity, good stability, and bioavailability, and they are promising structural motifs in drug design and development. Photoredox catalysis has clear benefits; it is a mild and sustainable methodology for the modification of chemical structures that enables a variety of chemical reactions that are unattainable using classical ionic chemistry. This review focuses on light-initiated trifluoromethylthiolation and trifluoromethylselenolation reactions with diverse SCF 3 and SeCF 3 reagents. Representative transformations either using photocatalysts or through EDA complexes, as well as possible reaction mechanisms, are all discussed in this article. 1 Introduction 2 Photocatalyzed Trifluoromethylthiolation 2.1 Photocatalyzed Trifluoromethylthiolation with MSCF 3 (M = H, [Me 4 N], Ag) 2.2 Photocatalyzed Trifluoromethylthiolation with XSCF 3 (X = Cl, CF 3 S) 2.3 Photocatalyzed Trifluoromethylthiolation with ArSO 2 SCF 3 2.4 Photocatalyzed Trifluoromethylthiolation with N–SCF 3 Reagents 2.5 Photocatalyzed Trifluoromethylthiolation with Other Reagents 3 Photocatalyzed Trifluoromethylselenolation 3.1 Photocatalyzed Trifluoromethylselenolation with [Me 4 N][SeCF 3 ] 3.2 Photocatalyzed Trifluoromethylselenolation with ArSO 2 SeCF 3 4 Summary [ABSTRACT FROM AUTHOR]

Catalytic ring-opening/functionalization of unactive cyclopropanes has proven to be a significant but challenging task in organic synthesis. Herein, we disclose the photoredox and cobalt cocatalyzed ring-opening/acceptorless dehydrogenative functionalization of monodonor cyclopropanes, which provides a promising platform to achieve a sustainable and atom-economic approach to assemble allylic N -acyl-acetal derivatives. The reaction features mild conditions, broad substrate scopes, and excellent functional group compatibilities. The optimized conditions accommodate various cycloalkylamides and primary, secondary, and tertiary alcohols, with applications in late-stage functionalization of pharmaceutically relevant compounds, stimulating the further utility in medicinal chemistry. Selective nucleophilic substitutions and further transformations of desired products with various carbon nucleophiles were succeed in a one-pot fashion, thus offering diverse acyclic or cyclic derivatives. 1 Introduction 2 Cooperative Photoredox and Cobalt-Catalyzed Dehydrogenative Functionalization of Allylic N -Acyl-acetal Derivatives 3 Mechanistic Study 4 Preliminary Studies of Asymmetric Transformation 5 Conclusion and Perspectives [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The direct reductive coupling of carbonyl compounds with propargyl halides is a powerful and reliable tool in the synthesis of α‐allenols. However, stoichiometric metal reductants, harsh reaction conditions and a variety of additional additives are required in the traditional strategies. Additionally, the reactivity and regioselectivity control remains an elusive challenge. Herein, we developed the Ti‐catalyzed regioselective reductive coupling of readily available aldehydes and racemic propargyl bromides to rapidly access a wide range of α‐allenols. This method proceed efficiently in a reductive radical‐polar crossover manner featuring mild conditions, excellent regioselectivity control, broad substrate scope, and eco‐friendliness. Preliminary mechanistic studies support the radical‐involved catalytic cycle. And the DFT calculations demonstrate that the regioselectivity is determined by the Zimmerman‐Traxler‐type transition states. [ABSTRACT FROM AUTHOR]

A new protocol for accessing 3,4-dihydroquinolin-2(1 H)-ones was established through a sequence of iron-catalyzed photoredox generation of carbamoyl radicals from oxamic acids, addition of the carbamoyl radicals to electron-deficient alkenes, intramolecular cyclization, and aromatization. The process is compatible with a variety of N -phenyloxamic acids and monosubstituted, 1,1-disubstituted, and trisubstituted electron-deficient alkenes. Employing cheap, readily available, and environmentally benign iron as the catalyst, the protocol provides an excellent alternative for synthesis of 3,4-dihydroquinolin-2(1 H)-ones. [ABSTRACT FROM AUTHOR]

In this study we report on the efficiency of a furane-indole-chromenone-based organic derivative (FIC) as a photocatalyst in the α-arylation of enol acetate upon LED irradiation at 405 nm, and as a photoinitiator/photocatalyst in the free radical polymerization of an acrylate group in the presence of bis-(4-tert-butylphenyl)iodonium hexafluorophosphate (Iod) as an additive, or in the presence of both Iod and ethyl-4-(dimethyl amino) benzoate (EDB) under LED irradiation at 365 nm. The photochemical properties of this new light-sensitive compound are described, and the wide redox window (3.27 eV) and the high excited-state potentials FIC*/FIC●− (+2.64 V vs. SCE) and FIC●+/FIC* (−2.41 V vs. SCE) offered by this photocatalyst are revealed. The chemical mechanisms that govern the radical chemistry are discussed by means of different techniques, including fluorescence-quenching experiments, UV-visible absorption and fluorescence spectroscopy, and cyclic voltammetry analysis. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed radical‐based enantioconvergent reactions have become a powerful strategy to synthesize enantiopure compounds from racemic starting materials. However, existing methods primarily address precursors with central chirality, neglecting those with axial chirality. Herein, we describe the enantioconvergent reductive coupling of racemic allenes with aldehydes, facilitated by a photoredox, chromium, and cobalt triple catalysis system. This method selectively affords one product from sixteen possible regio‐ and stereoisomers. The protocol leverages CoIII−H mediated hydrogen atom transfer (MHAT) and Cr‐catalyzed radical‐polar crossover for efficient stereoablation of axial chirality and asymmetric addition, respectively. Supported by mechanistic insights from control experiments, deuterium labeling, and DFT calculations, our approach offers synthetic chemists a valuable tool for creating enantioenriched chiral homoallylic alcohols, promising to advance radical‐based strategies for synthesizing complex chiral molecules. [ABSTRACT FROM AUTHOR]

The S-trifluoromethylation of thiols is accomplished using a simple and cost-effective organic catalyst (diacetyl) along with a bench-stable and environmentally friendly trifluoromethylating reagent (Langlois reagent). Under optimized conditions (2.5 equivalents of Langlois reagent, Blue LED irradiation, 48-h reaction time at room temperature), the reaction yielded up to 81% S-trifluoromethylated product. This method’s high yields, compatibility with a broad substrate scope (aliphatic, heteroaromatic, and aromatic thiols), and environmentally friendly conditions demonstrate its potential for broader synthetic applications. In contrast to traditional methods that rely on organometallic catalysts and environmentally hazardous reagents, this novel photoredox catalysis method offers a more economical and sustainable alternative for S-trifluoromethylation of thiols. [ABSTRACT FROM AUTHOR]

Carbohydrates are natural, renewable, chemical compounds that play crucial roles in biological systems. Thus, efficient and stereoselective glycosylation is an urgent task for the preparation of pure and structurally well‐defined carbohydrates. Photoredox catalysis has emerged as a powerful tool in carbohydrate chemistry, providing an alternative for addressing some of the challenges of glycochemistry. Over the last few decades, Ir‐ and Ru‐based organometallic photocatalysts have attracted significant interest because of their high stability, high‐energy triplet state, strong visible‐light absorption, long luminescence lifetime, and amenability to ligand modification. This review highlights the recent progress in the organometallic photocatalyst‐promoted synthesis and modification of carbohydrates under photoirradiation, as well as the related benefits and drawbacks. [ABSTRACT FROM AUTHOR]

Despite the preliminary success of transition metal‐catalyzed [3+2] annulation of amides with olefins, the corresponding radical‐type [3+2] annulation remains a laborious challenge. Herein we report the first photoredox‐catalyzed radical‐type [3+2] annulation of aromatic amides with olefins. We established an approach to generate unprecedented iminium radicals by reducing the oxyiminium intermediates, formed in situ from corresponding amides with Tf2O, via photoredox catalysis. The [3+2] annulation was achieved via stepwise radical process, instead of forming linear products via other pathways as previously reported. This annulation protocol exhibits excellent functional group tolerance, and a diversity of substrates are united under the photoredox conditions, affording iminium products that can be in situ diversified into 1‐indanones, enamines and amines. Mechanistic investigations indicate reduction of the oxyiminium intermediate to the iminium radicals by excited‐state of the photocatalyst initiates the catalytic cycle. [ABSTRACT FROM AUTHOR]

Reductive proton‐coupled electron transfer (PCET) has important energetic implications in numerous synthetic and natural redox processes. The development of catalytic systems that can mediate such transformations has become an attractive target, especially when light is used to generate the reactive species towards solar‐to‐chemicals conversion. However, such approach becomes challenged by kinetic competition with H2 evolution. Here we describe the excited state reactivity of a molecular Zr‐based platform under visible light irradiation for the efficient reduction of multiple bonds. Mechanistic investigations shine light on a charge separation process that colocalizes an excited electron and an acidic proton to promote selective PCET. We further leveraged this reactivity for the photocatalytic reduction of a variety of organic substrates. Our results demonstrate the promise of this molecular platform to design strong photocatalytic PCET mediators for reductive transformations. More broadly, we also show the potential relevance of PCET mechanisms in the (photo)redox chemistry of Zr‐based molecular materials. [ABSTRACT FROM AUTHOR]

In this work, the multi-step synthesis of three novel pyrimidopteridine photoredox catalysts is reported. These catalysts contain di(carboxyalkyl)-substitution at the 3- and 7-positions as handles for further synthetic modifications. The catalysts are fully characterized including by photochemical and electrochemical means. Additionally, a catalytic application in the oxidative annulation of 2-phenylbenzoic acid is presented. [ABSTRACT FROM AUTHOR]

Enzymes are natural treasure troves that hold multiple superiority. Enzymatic catalysis has become a powerful tool for asymmetric synthesis, though it is typically limited to a relatively narrow range of reaction types. By integrating the advantages of enzymatic catalysis with photocatalysis, photoenzymatic catalysis not only expands the catalytic capabilities of enzymes but also provides an effective strategy for the stereo‐control of photochemical reactions, thereby emerging as a significant research field. Herein, we focus on new‐to‐nature photoenzymatic catalysis by repurposing naturally occurring enzymes with visible light. We highlight the seminal work in reshaping various classes of enzymes, emphasizing their catalytic mechanism and synthetic potentials. Early Day Record: [ABSTRACT FROM AUTHOR]

The evolution of catalysis and functional group transfer reagents play a significant role in the development of anti‐Markovnikov alkene hydrofunctionalization reactions, facilitating the access to value‐added molecules. We herein report the first rational design of a modular intermolecular anti‐Markovnikov hydronitration of alkenes, enabling the direct synthesis of terminal nitroalkanes under visible light‐mediated photoredox catalysis. By employing the redox‐active organic nitrating reagent N‐nitrosuccinimide, the produced nitryl radicals, in the presence of an olefin and a hydrogen atom transfer (HAT) mediator, lead to an anti‐Markovnikov addition with complete regioselectivity. Furthermore, we present results demonstrating the use of this catalytic system for chain expansion via anti‐Markovnikov addition, utilizing substituted bromonitroalkanes as commercially available reagents. These transformations effectively address a gap in synthetic chemistry, enabling the direct synthesis of nitroalkanes from a variety of unactivated olefins in both complex molecules and unfunctionalized commodity chemicals. [ABSTRACT FROM AUTHOR]

The triplet excited state lifetime of a photosensitizer is an essential parameter for diffusion‐controlled energy‐ and electron‐transfer, which occurs usually in a competitive manner to the intrinsic decay of a triplet excited state. Here we show the decisive role of luminescence lifetime in the triplet excited state reactivity toward energy‐ and electron transfer. Anchoring two phenyl anthracene chromophores to a ruthenium(II) polypyridyl complex (RuII ref) leads to a RuII triad with a luminescence lifetime above 100 μs, which is more than 40 times longer than that of the prototypical complex. The obtained RuII triad sensitizes energy transfer to anthracene‐based annihilators more efficiently than RuII ref and enables red‐to‐blue photon upconversion with a pseudo anti‐Stokes shift of 0.94 eV and a moderate upconversion efficiency near 1 % in aerated solution. Particularly, RuII triad allows rapid photoredox catalytic polymerizations of acrylate and acrylamide monomers under aerobic condition with red light, which are kinetically hindered for RuII ref. Our work shows that excited state lifetime of a photosensitizer governs the dynamics of the excited state reactions, which seems an overlooked but important aspect for photochemistry. [ABSTRACT FROM AUTHOR]

Visible‐light induced selective arylation of 2‐imino‐2H‐chromene‐3‐carbonitriles and decarboxylative ipso‐arylation of coumarin‐3‐carboxylic acids have been accomplished under mild conditions in the absence of either base or acid and oxidant. By employing blue LEDs as an excitation source, the aryl radicals are generated by Ru(II) complex through a single‐electron transfer process, which subsequently react with 2‐imino‐2H‐chromene‐3‐carbonitriles and 2‐oxo‐2H‐chromene‐3‐carboxylic acids to produce the desired products. This is the first report on selective arylation of conjugated systems without using either an acid or a base. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: α‐Azaarene quaternary carbon centers are prevalent in drug molecules, making the development of efficient synthetic approaches of great interest. Herein, we describe an unprecedented method for constructing α‐all‐carbon quaternary carbon‐centered azaarenes by employing photocatalytic reductive coupling of various 2,2‐disubstituted cycloproarylketones with readily available cyanoazaarenes. The reaction proceeds with high efficiency, displaying excellent compatibility with various functional groups and demonstrating high chemo‐ and regioselectivity. Mechanistic investigations suggest that consecutive photo‐induced electron transfer (ConPET) plays a crucial role in the formation of photocatalyst with greater reducing capability, ultimately enabling the direct reductive conversion of unreactive π‐bonds under mild and transition‐metal‐free conditions. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: α‐Azaarene quaternary carbon centers are prevalent in drug molecules, making the development of efficient synthetic approaches of great interest. Herein, we describe an unprecedented method for constructing α‐all‐carbon quaternary carbon‐centered azaarenes by employing photocatalytic reductive coupling of various 2,2‐disubstituted cycloproarylketones with readily available cyanoazaarenes. The reaction proceeds with high efficiency, displaying excellent compatibility with various functional groups and demonstrating high chemo‐ and regioselectivity. Mechanistic investigations suggest that consecutive photo‐induced electron transfer (ConPET) plays a crucial role in the formation of photocatalyst with greater reducing capability, ultimately enabling the direct reductive conversion of unreactive π‐bonds under mild and transition‐metal‐free conditions. [ABSTRACT FROM AUTHOR]

Transition metal-catalyzed cross-coupling with aryl halides has revolutionized the way of diversifying aromatic compounds. Aryl ethers are attractive alternatives to aromatic halides as coupling partners considering the accessibility and potential environmental benefits. The last two decades have witnessed a striking success in the field of C–O bond activation of aryl ethers, including the construction of C–C bond and C–X bond, as well as reductive deoxygenation. Here, we present a comprehensive review of C–O bond activation in the context of aryl, vinyl, and benzylic ethers. This review elaborates on the current state-of-the-art methods, categorized by different catalytic systems, including transition metal catalysis, photoredox catalysis, and other innovative approaches. The newly developed methods allow C–O bond activation under mild conditions with exceptional functional group tolerance, potentially enabling the late-stage functionalization of pharmaceuticals. The limitations and future perspectives of the methods are also presented. [ABSTRACT FROM AUTHOR]

Herein, we report the development of a FSO2 radical initiated tandem cyclization reaction under visible light photoredox catalysis, which allows for a facile access to FSO2-functionalized oxindoles from N -arylacrylamides. This reaction features mild reaction conditions, readily available starting materials, and SuFExable products. The introduction of sulfonyl fluoride groups into oxindoles could be of interest for related study in the context of discovering new bioactive molecules. [ABSTRACT FROM AUTHOR]

The direct nucleophilic addition of amides to unfunctionalized alkenes via photoredox catalysis represents a facile approach towards functionalized alkylamides. Unfortunately, the scarce nucleophilicity of amides and competitive side reactions limit the utility of this approach. Herein, we report an intramolecular photoredox cyclization of alkenes with β-lactams in the presence of an acridinium photocatalyst. The approach uses an intramolecular nucleophilic addition of the β-lactam nitrogen atom to the radical cation photogenerated in the linked alkene moiety, followed by hydrogen transfer from the hydrogen atom transfer (HAT) catalyst. This process was used to successfully prepare 2-alkylated clavam derivatives.

Comprehensive Summary An efficient transannular cyano migration is reported for gem‐dicyano‐1,6‐diene, which is triggered by the addition of external arylsulfonyl radicals. The overall transformation proceeds through a sequence of intramolecular 5‐exo‐trig cyclization, suprafacial 1,4‐cyano migration, and the capture by H or D atom, leading to the production of valuable polysubstituted cyclopentanes under mild photoredox catalytic conditions. The reaction is adapted to a wide range of sodium (hetero)arylsulfinates, demonstrating good functional group compatibility. This method provides a new protocol for radical‐mediated functional group migration. [ABSTRACT FROM AUTHOR]

Photo‐driven cross‐coupling of o‐arylenediamines and alcohols has emerged as an alternative for the synthesis of bio‐active benzimidazoles. However, tackling the key problem related to efficient adsorption and activation of both coupling partners over photocatalysts towards activity enhancement remains a challenge. Here, we demonstrate an efficient interface synergy strategy by coupling exposed oxygen vacancies (VO) and Pd Lewis acid sites for benzimidazole and hydrogen (H2) coproduction over Pd‐loaded TiO2 nanospheres with the highest photoredox activity compared to previous works so far. The results show that the introduction of VO optimizes the energy band structure and supplies coordinatively unsaturated sites for adsorbing and activating ethanol molecules, affording acetaldehyde active intermediates. Pd acts as a Lewis acid site, enhancing the adsorption of alkaline amine molecules via Lewis acid‐base pair interactions and driving the condensation process. Furthermore, VO and Pd synergistically promote interfacial charge transfer and separation. This work offers new insightful guidance for the rational design of semiconductor‐based photocatalysts with interface synergy at the molecular level towards the high‐performance coproduction of renewable fuels and value‐added feedstocks. [ABSTRACT FROM AUTHOR]

Herein, we report a facile and efficient deuteration degree controllable method for the preparation of aryl deuteromethyl ethers through dual photoredox and thiol catalysis using phenols as the starting materials and inexpensive D2O and CDCl3 as the deuterium sources. All aryl d1, d2, and d3 deuteromethyl ethers can be precisely prepared with good to excellent yields and deuteration ratios. The reaction operates under mild conditions without the need for high temperatures or high loading of transition metal catalysts, and a wide range of functional groups are well tolerated. [ABSTRACT FROM AUTHOR]

We describe the use of acyl imidazoles derived from aliphatic carboxylic acids for the N-heterocyclic carbene/organic photoredox co-catalyzed meta -selective functionalization of electron-rich arenes. Compared to our previous work, a change of the wavelength of the applied LED light from 440 nm to 390 nm promotes this reaction efficiently. [ABSTRACT FROM AUTHOR]

The extensive use of pesticides to ensure global food production presents significant threats to both human health and the environment. In this study, the photochemical, redox, and acid‐base properties of Zr‐metal‐organic polyhedra (Zr‐MOP) and polyoxometalates (POM) are utilized to fabricate functional hybrid salts, denoted as [Zr‐MOP][POM], designed for pesticide detoxification. Upon light irradiation, [Zr‐MOP][POM] salts generate a charge‐separated state with oxidizing properties. This activated state selectively photooxidizes highly toxic and persistent fenamiphos into fenamiphos sulfoxide and subsequently hydrolytically breaks down it into non‐toxic 3‐methyl‐4‐(methylsulfinyl)phenol and phosphate components. The hydrolytic degradation of fenamiphos is facilitated by the reduced basicity of the 3‐methyl‐4‐(methylsulfinyl)phenolate residue (ΔpKb = ‐2.4) in the photooxidized form of the pesticide molecule. Furthermore, the hybrid salts demonstrate efficacy in the breakdown of multicomponent pesticide mixtures such as fenamiphos and methylparaoxon. [ABSTRACT FROM AUTHOR]

We report the photocatalytic oxidation of α‐carbonyl radicals of amides or esters to the corresponding α‐carbonyl carbocations through super photoreductant CBZ6 induced redox‐neutral photocatalysis. The α‐carbonyl radicals are formed by the β‐addition of alkyl radicals generated in situ by the photocatalytic fragmentation of N‐hydroxyphthalimide esters to the α,β‐unsaturated amides and esters. This method enables the α‐nucleophilic addition of hydroxyl or alkoxyl radicals to amides and esters without any prefunctionalization. [ABSTRACT FROM AUTHOR]

Based on rational design, benzoyl cyanide, a well-known ionic acylating reagent, has been developed as a general radical acylating reagent for benzylic site-selective acylation reactions for the first time. Using visible-light photoredox-catalyzed single electron transfer (SET) and hydrogen atom transfer (HAT) strategies, two different direct benzylic C–H acylation reactions with high atom economy have been developed. This newly developed radical acylating reagent could also be used to achieve three component acyltrifluoromethylation of styrenes, which is usually challenging to achieve by other means. All of these reactions proceed under mild nickel-free and NHC-free conditions with high functional group tolerance. In addition, based on our detailed mechanistic experiments, the process of radical-radical cross-coupling mechanism was suggested for these transformations. [ABSTRACT FROM AUTHOR]

Selective functionaliz0ation of C(sp3)–H bonds is a straightforward and practical method to construct complex molecule skeletons. In this field, direct transformation of unactivated C(sp3)–H bonds into C(sp3)–SCF3 architectures is still a great challenge. We report a highly selective trifluoromethylthiolation of unactivated aliphatic C(sp3)–H bonds by combination of proton-coupled electron transfer (PCET) and hydrogen atom transfer (HAT) strategy. A wide range of structurally diverse alkyl trifluoromethyl sulfides are obtained. Furthermore, the use of two different photocatalysts can realize an unprecedented trifluoromethylthiolation and amidation cascade of different C(sp3)–H bonds. It can afford a good access to bifunctionalized molecules in synthetically useful yields. [ABSTRACT FROM AUTHOR]

Radical-involved allylation reactions have emerged as a powerful platform for construction of carbon-carbon and carbonheteroatom bonds, facilitating the strategic incorporation of diverse allyl moieties. Nevertheless, this burgeoning field still faces ongoing challenges, including limitations of radical precursors and coupling partners, and difficulties in achieving enantiocontrol. Herein, we report for the first time a highly enantioselective radical allylation involving β-keto esters with vinyl cyclopropanes utilizing a synergistic dual photoredox/nickel catalysis under visible light irradiation. The mild and redox-neutral catalytic protocol demonstrates an extensive substrate compatibility and good functional tolerance, providing access to enantioenriched β-keto esters featuring quaternary α-stereocenter with good yields and high enantioselectivities. Preliminary mechanistic studies have uncovered that the success of the reaction hinges on the dual roles of nickel catalyst, including in situ formation of photoredox sensitive substrate/Ni complex and the ensuing asymmetric radical addition step. [ABSTRACT FROM AUTHOR]

Isomerisation reactions provide streamlined routes to organic compounds which are otherwise hard to directly synthesise. The most common forms are positional, geometrical or stereochemical isomerisations which involve the relocation of a double bond or a change in relative location of groups in space. In contrast, far fewer examples of structural (or constitutional) isomerisation exist where the connectivity between atoms is altered. The development of platforms capable of such rearrangement poses a unique set of challenges because chemical bonds must be selectively cleaved, and new ones formed without overall addition or removal of atoms. Here, we show that a dual catalytic system can enable the structural isomerisation of readily available allylic alcohols into more challenging‐to‐synthesise α‐arylated ketones via a H‐atom transfer initiated semi‐pinacol rearrangement. Key to our strategy is the combination of a cobalt catalyst and photocatalyst under reductive, protic conditions which allows intermediates to propagate catalytic turnover. By providing an unusual disconnection to structural motifs which are difficult to access through direct arylation, we anticipate inspiring other advanced catalytic isomerisation strategies that will further retrosynthetic logic for complex molecule synthesis. [ABSTRACT FROM AUTHOR]

C(sp3)‐rich heterocycles are privileged building blocks for pharmaceuticals and agrochemicals. Therefore, synthetic methods that provide access to novel saturated nitrogen‐containing heterocycles are in high demand. Herein, we report a general synthesis of 1‐azabicyclo[2.1.1]hexanes (1‐aza‐BCH) via a formal cycloaddition of azabicyclo[1.1.0]butanes (ABB) with styrenes under photochemical conditions. To overcome the challenging direct single electron reduction of ABBs, we designed a polar‐radical‐polar relay strategy that leverages a fast acid‐mediated ring‐opening of ABBs to form bromoazetidines, which undergo efficient debrominative radical formation to initiate the cycloaddition reaction. The reaction is applicable to a broad range of ABB‐ketones and we demonstrate the 1‐aza‐BCH products can be further functionalized to access larger saturated, conformationally rigid heterocycles. [ABSTRACT FROM AUTHOR]

A visible‐light triplet photocatalyst 5‐acetyl‐2‐mercapto‐benzoic acid methyl ester (AcBSH) was developed through introducing acetyl into benzenethiolate to improve the efficiency of intersystem crossing (ISC) and using o‐methoxyformyl to increase the molar extinction coefficient. In the photocatalytic system of AcBSH, the reductive dearomatization of N‐arylformylindoles is achieved to afford the desired indolines in moderate to excellent yields, including both indoles without (1) and with 2‐substituent (2). The 2‐substituent is a steric hindrance for the conjugation between benzoyl and indole moiety, and makes indole 2 and indole 1 exhibit different reduction potentials (Ered) and different triplet energy levels (ΔET). Thereby, two kinds of substrates undergo primarily two photocatalytic pathways: i) successive SET/protonation pathway, which merging photosensitization via triplet‐triplet energy transfer (EnT) and photoinduced SET for substrates 1, and ii) single electron transfer (SET) from the triplet photocatalyst and a concerted hydrogen atom transfer (HAT) process for substrates 2. [ABSTRACT FROM AUTHOR]

Radical‐involved arylative cross‐coupling reactions have recently emerged as an attractive strategy to access valuable aryl‐substituted motifs. However, there still exist several challenges such as limited scope of radical precursors/acceptors, and lack of general asymmetric catalytic systems, especially regarding the multicomponent variants. Herein, we reported a general copper‐Box system for asymmetric three‐component arylative radical cross‐coupling of vinylarenes and 1,3‐enynes, with oxime carbonates and aryl boronic acids. The reactions proceed under practical conditions in the absence or presence of visible‐light irradiation, affording chiral 1,1‐diarylalkanes, benzylic alkynes and allenes with good enantioselectivities. Mechanistic studies imply that the copper/Box complexes play a dual role in both radical generation and ensuing asymmetric cross‐coupling. In the cases of 1,3‐enynes, visible‐light irradiation could improve the activity of copper/Box complex toward the initial radical generation, enabling better efficiency match between radical formation and cross‐coupling. [ABSTRACT FROM AUTHOR]

Visible light‐driven photocatalytic deracemization is highly esteemed as an ideal tool for organic synthesis due to its exceptional atom economy and synthetic efficiency. Consequently, successful instances of deracemization of allenes have been established, where the activated energy of photosensitizer should surpass that of the substrates, representing an intrinsic requirement. Accordingly, this method is not applicable for axially chiral molecules with significantly high triplet energies. In this study, we present a photoredox catalytic deracemization approach that enables the efficient synthesis of valuable yet challenging‐to‐access axially chiral 2‐azaarene‐functionalized quinazolinones. The substrate scope is extensive, allowing for both 3‐axis and unmet 1‐axis assembly through facile oxidation of diverse central chiral 2,3‐dihydroquinazolin‐4(1H)‐ones that can be easily prepared and achieve enantiomer enrichment via deracemization. Mechanistic studies reveal the importance of photosensitizer selection in attaining excellent chemoselectivity and highlight the indispensability of a chiral Brønsted acid in enabling highly enantioselective protonation to accomplish efficient deracemization. [ABSTRACT FROM AUTHOR]

The glycosylation of peptides and proteins can significantly impact their intrinsic properties, such as conformation, stability, antigenicity, and immunogenicity. Current methods for preparing N‐linked glycopeptides typically rely on amide bond formation, which can be limited by the presence of reactive functional groups like acids and amines. Late‐stage functionalization of peptides offers a promising approach to obtaining N‐linked glycopeptides. In this study, we demonstrate the preparation of N‐linked glycopeptides through a photoredox‐catalyzed site‐selective Giese addition between N‐glycosyl oxamic acid and peptides containing dehydroalanine (Dha) under visible light conditions. Unlike traditional methods that rely on the coupling of aspartic acid and glycosylamine, this approach utilizes the conjugation of N‐glycosylated carbamoyl radicals with Dha, facilitating the straightforward modification of complex peptides. [ABSTRACT FROM AUTHOR]

Mediated electron transfer (MET) is fundamental to many biological functions, including cellular respiration, photosynthesis, and enzymatic catalysis. However, leveraging the MET process to enable the release of therapeutic gases has been largely unexplored. Herein, we report the bio‐inspired activation of a series of UV‐absorbing N‐nitrosamide derivatives (NOA) under red light exposure, enabling the quantitative release of nitric oxide (NO) gasotransmitter via an MET process. The cornerstone of our design is the covalent linkage of a 2,4‐dinitroaniline moiety, which acts as an electron mediator to the N‐nitrosamide groups. This facilitates efficient electron transfer from the excited palladium(II) meso‐tetraphenyltetrabenzoporphyrin (PdTPTBP) photocatalyst and the selective activation of NOA. Our approach has been validated with distinct photocatalysts and various N‐nitrosamides, including those derived from carbamates, amides, and ureas. Notably, the modulation of the linker length between the electron mediator and N‐nitrosamide groups serves as a regulatory mechanism for controlling NO release kinetics. Moreover, this biomimetic NO release platform demonstrates effective operation under both normoxic and hypoxic conditions, and it enables localized delivery of NO under physiological conditions, exhibiting significant anticancer efficacy within the phototherapeutic window and enhanced selectivity towards tumor cells. [ABSTRACT FROM AUTHOR]

Photocatalysis holds a pivotal position in modern organic synthesis, capable of inducing novel reactivities under mild and environmentally friendly reaction conditions. However, the merger of photocatalysis and transition‐metal‐catalyzed asymmetric C−H activation as an efficient and sustainable method for the construction of chiral molecules remains elusive and challenging. Herein, we develop a cobalt‐catalyzed enantioselective C−H activation reaction enabled by visible‐light photoredox catalysis, providing a synergistic catalytic strategy for the asymmetric dearomatization of indoles with high levels of enantioselectivity (96 % to >99 % ee). Mechanistic studies indicate that the excited photocatalyst was quenched by divalent cobalt species in the presence of Salox ligand, leading to the formation of catalytically active chiral Co(III) complex. Moreover, stoichiometric reactions of cobaltacycle intermediate with indole suggest that the irradiation of visible light also play a critical role in the dearomatization step. [ABSTRACT FROM AUTHOR]

The modular synthesis of diverse carbonyl compounds is at the heart of organic synthesis. An optimized protocol for photoredox carbonylation was developed that operates under milder conditions with mesitylacridinium as a photocatalyst. Arenediazonium salts were converted into benzoates (with alcohols), benzoic acids (with water), benzamides (with amines), and chlorides (with 1-butyl-3-methylimidazolium chloride) at 20 bar CO and 20 °C. [ABSTRACT FROM AUTHOR]

Difluoroalkyl sulfide (‐CF2S‐) moieties are an important class of skeletons in medicinal chemistry. Herein, a photoredox radical‐polar crossover reaction is reported for the three‐component thiofluorination, thiohydroxylation, thioalkoxylation, thioaminolation, and thiochlorination of gem‐difluoroalkenes towards diverse α‐functionalized difluoroalkyl sulfides. Such an approach features mild conditions, operational simplicity, and good substrate scope. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A visible‐light‐induced photoredox‐catalyzed regioselective and stereoselective C(sp2)–H amination of enamides with bench‐stable and easily accessible N‐aminopyridium salts is developed, affording synthetically and biologically prominent vicinal 1,2‐diamine scaffolds with broad substrate scope and excellent functional group compatibility. The transformation proceeded through a radical pathway involving the Giese addition of the relatively electrophilic N‐centered sulfonamidyl radical species to nucleophilic β‐olefinic position of enamides followed by the ensuing single electron oxidation and β‐H elimination, delivering geometrically‐defined Z‐configured β‐sulfonamidylated enamides. The operational simplicity, environmental friendliness and cost efficiency of this methodology allowed it to pave a new avenue to enrich the arsenal of synthetically crucial functionalized enamides and their related derivatives. [ABSTRACT FROM AUTHOR]

Over the past decades, visible light‐mediated photocatalysis has found a mainstream of applications in synthetic chemistry. Organosilanes have been proven to be a useful class of electron donors to generate the highly active radical species via photoinduced single electron transfer oxidation/fragmentation sequence, which may undergo follow‐up radical coupling or addition process. This minireview highlights the comprehensive advances of organosilanes in photoredox catalyzed asymmetric organic synthesis, with particular emphasis placed on reaction mechanisms. We hope that this review will inspire further design and development of new reactions with such class of readily accessible reagents. [ABSTRACT FROM AUTHOR]

The facile generation of the α‐acyloxy carboxamide radical is hereby reported for the first time, utilizing a photoredox catalyzed reaction of Passerini adducts synthesized using a 4‐formyl‐1,4‐dihydropyridine as the carbonyl component. This radical effectively engages in a Giese reaction with a range of olefins, ultimately leading to the synthesis of novel Passerini‐derived products not previously amenable to direct aldehyde‐based transformations. Consequently, the resulting strategy, developed both in batch and in flow, offers a promising opportunity to expand the chemical space accessible through the Passerini reaction, virtually incorporating "impossible" aldehydes. [ABSTRACT FROM AUTHOR]

Photoredox catalysis has become an invaluable tool for the construction of organic molecules, allowing for unparalleled control over radical intermediates enabled by the mild conditions achieved through visible-light activation of a photocatalyst. These reactions can be classified under two distinct mechanistic paradigms: closed photocatalytic cycles, and photoinitiated chain reactions. While optimization strategies for each of these classes of reaction differ significantly, organic chemists still lack a straightforward means for probing chain-propagation. In this work, we report a simple and accessible approach to performing intermittent illumination studies for characterizing chain reactions in photoredox catalysis. Using modern LED technologies to precisely control the rate of sample illumination, we were able to validate the presence or absence of product-forming chain reactions in four previously reported photoredox protocols. Furthermore, this technique also allows for the determination of chain-propagating lifetimes through a simple graphical analysis. Given the operational simplicity and ease of accessibility, we believe this intermittent illumination technique will be of great value to practitioners of the field moving forward.