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Herein, we describe an effective method for the synthesis of 2-alkoxyamides and 1,2-diamines through visible-light-mediated difunctionalization of alkenes. N -Aminopyridinium salts were employed as appropriate precursors to generate key amidyl radical intermediates via a photoinduced single-electron transfer (SET) process. The amidyl radicals would react with alkenes, followed by oxidation and nucleophilic addition. Excellent functional group tolerance and good yields demonstrate the synthetic potential of this transformation.

A visible-light-promoted research protocol for constructing dihydropyrido[1,2- a ]indolone skeletons is herein described proceeding through a cascade cyclization mediated by trifluoromethyl radicals. This method allows the efficient synthesis of various indole derivatives without the need of photocatalysts or transition-metal catalysts. Mechanism experiments indicate that the process involves a radical chain process initiated by the homolysis of Umemoto's reagent. This straightforward method enables a rapid access to heterocycles containing a trifluoromethyl group., (Copyright © 2024, Yang et al.)

A catalyst-free approach for the multicomponent aminoheteroarylation reaction of alkenes with N -aminopyridinium salts and heteroarenes is herein described. The reaction shows good functional group tolerance and allows the generation of valuable β-heteroarylethylamines in satisfying yields. In this transformation, N -aminopyridinium salts and heteroarenes are utilized to generate electron donor-acceptor complexes, which undergo a single-electron transfer process upon light irradiation to form key amidyl radicals and heteroaryl radical cations. The amidyl radical is subsequently captured by alkenes, followed by a Minisci-type reaction to yield the desired β-heteroarylamines as products.

Organoboron compounds are of high significance in organic synthesis due to the unique versatility of boryl substituents to access further modifications. The high demand for the incorporation of boryl moieties into molecular structures has witnessed significant progress, particularly in the C(sp 3 )-H borylation of hydrocarbons. Taking advantage of special characteristics of photo/electrochemistry, we herein describe the development of an oxidative C(sp 3 )-H borylation reaction under metal- and oxidant-free conditions, enabled by photoelectrochemical strategy. The reaction exhibits broad substrate scope (>57 examples), and includes the use of simple alkanes, halides, silanes, ketones, esters and nitriles as viable substrates. Notably, unconventional regioselectivity of C(sp 3 )-H borylation is achieved, with the coupling site of C(sp 3 )-H borylation selectively located in the distal methyl group. Our method is operationally simple and easily scalable, and offers a feasible approach for the one-step synthesis of high-value organoboron building blocks from simple hydrocarbons, which would provide ample opportunities for drug discovery., (© 2023. Springer Nature Limited.)

The first total syntheses of polycyclic diterpenes phomopsene ( 1 ), methyl phomopsenonate ( 2 ), and iso -phomopsene ( 3 ) have been accomplished through the unusual cascade reorganization of C-C single bonds. This approach features: (i) a synergistic Nazarov cyclization/double ring expansions in one-step, developed by authors, to rapid and stereospecific construction of the 5/5/5/5 tetraquinane scaffold bearing contiguous quaternary centers and (ii) a one-pot strategic ring expansion through Beckmann fragmentation/recombination to efficiently assemble the requisite 5/5/6/5 tetracyclic skeleton of the target molecules 1 - 3 . This work enables us to determine that the correct structure of iso -phomopsene is, in fact, the C7 epimer of the originally assigned structure. Finally, the absolute configurations of three target molecules were confirmed through enantioselective synthesis.

β-(Hetero)arylethylamines are privileged structural motifs found in many high-value organic molecules, including pharmaceuticals and natural products. To construct these important molecular skeletons, previous methods are mainly achieved by amino(hetero)arylation reaction with the aid of transition metals and preactivated substrates. Herein, we report a metal-free and photoinduced intermolecular amino(hetero)arylation reaction for the single-step installation of both (hetero)aryl and iminyl groups across alkenes in an efficient and regioselective manner. This method shows broad scope (up to 124 examples) and excellent tolerance of various olefins─from the simplest ethylene to complex multisubstituted alkenes can all participate in the reaction. Furthermore, aminosulfonylation of alkenes can be also conducted in the presence of sodium bisulfite as the SO 2 source.

Herein, a visible light-induced synthesis of polysubstituted oxazoles from diazo compounds is reported. This developed synthetic method differs from traditional routes that rely on transition metals and external chemical oxidants. Our method uses readily available and inexpensive diazonium compounds as well as nitrile substrates with a catalytic amount of (i-Pr) 3 SiCl species, delivering the corresponding valuable multi-substituted oxazole products (up to 95% yield). This protocol exhibits a broad substrate scope and is easily carried out under mild reaction conditions. Notably, gram-scale synthesis in a continuous flow fashion has been performed.

An electrochemical nickel catalyzed hydroarylation reaction of various alkynes is herein described. In this reaction, alkynes were coupled with aryl iodides by electrochemical Ni catalysis to obtain highly selective trans -olefins. The outstanding features of this protocol include mild reaction conditions, operational simplicity, and excellent functional group tolerance.

A visible-light-induced trifluoromethylsulfonylation reaction of diazo compounds is herein reported. This developed synthetic method captures the relatively rare trifluoromethyl sulfone radicals via coordination to the Mn(acac) 3 catalyst, delivering the corresponding α-trifluoromethyl sulfone esters in good to moderate yields (up to 82%). This protocol exhibits broad substrate scope and is easily carried out under mild reaction conditions. Furthermore, a plausible mechanism of the reaction was investigated through DFT calculations.

Catalytic C(sp 3 )-H functionalization has provided enormous opportunities to construct organic molecules, facilitating the derivatization of complex pharmaceutical compounds. Within this framework, direct hydrogen atom transfer (HAT) photocatalysis becomes an appealing approach to this goal. However, the viable substrates utilized in these protocols are limited, and the site selectivity shows preference to activated and thermodynamically favored C(sp 3 )-H bonds. Herein, we describe the development of undirected iron-catalyzed C(sp 3 )-H borylation, thiolation, and sulfinylation reactions enabled by the photoinduced ligand-to-metal charge transfer (LMCT) process. These reactions exhibit remarkably broad substrate scope (>150 examples in total), and most importantly, all of these three reactions show unconventional regioselectivity, with the occurrence of C(sp 3 )-H borylation, thiolation, and sulfinylation preferentially at the distal methyl position. The procedures are operationally simple and readily scalable and provide access to high-value products from simple hydrocarbons in one step. Mechanistic studies and control experiments indicate that the afforded site selectivity is not only relevant to the HAT species but also largely affected by the use of boron- and sulfone-based radical acceptors.

A versatile photochemical ring-expansion protocol for the synthesis of oxacyclic spirooxindoles under catalyst-free conditions is described. The reaction is enabled by the use of unstrained O-containing heterocycles with 3-diazoindolin-2-ones under visible-light irradiation. Several synthetic advantages for this method are exhibited, including mild conditions, good functional group tolerance, operational simplicity, and scalability. Mechanistic studies indicate that the transformation may proceed through the formation of oxonium ylide intermediate followed by an ionic cyclization.

We report a vinyl radical-mediated 1,5-hydrogen atom transfer (1,5-HAT) strategy for the remote C(sp 3 )-H functionalization reaction, which includes cyanation, oxidation, and etherification under visible-light-induced photochemical conditions. This reaction is achieved using readily available alkyl N -hydroxyphthalimide esters as radical precursors, which can efficiently react with diverse alkynes to form key vinyl radical intermediates followed by a 1,5-HAT process. A series of structurally diverse γ-cyano, γ-carbonyl, and γ-oxygenated alkenes with excellent stereoselectivity can be efficiently constructed by this synthetic protocol.

The electrochemical deconstructive functionalization of cycloalkanols with nucleophiles has been studied, which allows functionalization to occur exclusively at the β-position of ketones. The substrate scope includes a wide range of cycloalkanols as well as diverse N, O, C, and P-centered nucleophiles, providing ready access to β-functionalized ketones as products. Mechanistic studies support the generation of α,β-unsaturated ketones as key intermediates followed by Michael addition with nucleophiles.

The photoinitiated deaminative [3 + 2] annulation reaction of N -aminopyridinium salts with alkenes for the synthesis of functionalized γ-lactams is described. This transformation shows good functional group tolerance as well as excellent diastereoselectivity. Preliminary studies suggest that the employed N -aminopyridinium salts generate the key amidyl radical intermediates through N-N bond cleavage via a photoinduced single-electron transfer (SET) process. The amidyl radical species would add to the double bond of alkenes, followed by a radical-mediated annulation process, to afford the desired γ-lactams.

A transition metal-free photoredox cascade cyclization is herein reported. In this protocol, sustainable visible light was used as the energy source and organic light-emitting molecule eosin Y served as an efficient photocatalyst. A variety of easily available 2-aryl- N -acryloyl indoles can readily react with alkyl radicals, which are generated from organohalides and tertiary amines via either the halogen-atom-transfer (XAT) or the hydrogen-atom-transfer (HAT) process, furnishing the desired indolo[2,1-α]isoquinoline derivatives in good to moderate yields. This protocol features broad substrate scope and good functional group tolerance under mild conditions.

A visible-light-induced multicomponent reaction of ethyl diazoacetate, diarylamines, and styrene-type alkenes is described. This novel 1,2-difunctionalization of alkenes can be readily achieved under a simple operation and mild conditions, affording γ-amino esters as major products. The reaction proceeds through the generation of carbon-centered radicals from diazo compounds by a visible-light-promoted proton-coupled electron transfer (PCET) process. The carbon radicals then add to diverse alkenes, delivering new carbon radical species, and the final products are formed with N -centered radicals via a radical-radical coupling.

A multicomponent carbonyl alkylative amination reaction is described. A variety of N -arylamines, aldehydes, and hydrocarbons have been examined as reaction substrates using tetrabutylammonium decatungstate as photocatalyst, providing the corresponding α-branched tertiary and secondary amines in good to moderate yields. The reaction proceeds through the generation of alkyl radicals by a light-promoted hydrogen atom transfer process followed by free radical addition to iminium ions generated in situ.

An electroreductive arylation reaction of aliphatic and aromatic aldehydes as well as ketones with electro-deficient (hetero)arenes is described. A variety of cyano(hetero)arenes and carbonyl compounds, especially aliphatic aldehydes, have been examined, providing secondary and tertiary alcohols in moderate to good yields. Mechanistic studies, including cyclic voltammetry (CV), electron paramagnetic resonance (EPR), and divided-cell experiments, support the generation of aliphatic ketyl radicals and persistent heteroaryl radical anions via cathodic reduction followed by radical-radical cross-coupling.

A palladium-catalyzed Narasaka-Heck reaction by a domino cross-coupling reaction with aromatic alkenes under blue LED irradiation at room temperature was developed. The undesired β-hydride elimination of the hybrid alkyl palladium radical species was prohibited, enabling a broad range of oxime esters to undergo 5-exo cyclization and subsequent coupling with olefins. The practicality of the method was well illustrated by the construction of a nitrogen bridgehead tricycle as a core skeleton of alkaloids.

Herein, we describe a visible light-promoted hydroacylation strategy that facilitates the preparation of ketones from alkenes and 4-acyl-1,4-dihydropyridines via an acyl radical addition and hydrogen atom transfer pathway under photocatalyst-free conditions. The efficiency was highlighted by wide substrate scope, good to high yields, successful scale-up experiments, and expedient preparation of highly functionalized ketone derivatives. In addition, this protocol allows for the synthesis of 1,4-dicarbonyl compounds through alkene diacylation in the presence of NiCl 2 ·DME.

A novel strategy to trap iminyl radicals with copper ions has been developed at room temperature, the resulted high-valent Cu(III) imine intermediate resets quickly to form nitrene and then to furnish a 2 H -azirine. This protocol with dual copper/photoredox catalyst enables the selective imination of unactivated C-H bonds under mild conditions with a broader scope. Moreover, this method also uncovers a novel ring-expansion rearrangement from cyclobutyl oxime derivatives to give the α-acylamino cyclopentanones.

A direct defluorinative multifluoroarylation of unactivated sp 3 C-H bonds through hydrogen atom transfer using photoredox catalysis has been developed. The C(sp 3 )-C(sp 2 ) couplings between C(sp 2 )-F bonds and corresponding C(sp 3 )-H bonds adjacent to heteroatoms proceeded smoothly to afford the desired products in moderate to good yields. Preliminary mechanistic investigations on this novel transformation revealed that the C-H cleavage process might be involved in the rate-determining step.

Alkylated (hetero)arenes constitute one of the most fundamental skeletons in organic molecules, which prompts a growing number of research studies on the construction of (hetero)aryl C(sp 2 )-C(sp 3 ) bonds especially using C-H bonds of feedstocks. With the flourishing resurgence of photoredox catalysis in organic synthesis, fruitful achievements have been witnessed in photochemical (hetero)aryl C(sp 2 )-C(sp 3 ) bond formation through C-H bond coupling such as (hetero)arylation of C(sp 3 )-H bonds and alkylation of (hetero)aryl C(sp 2 )-H bonds. Photoinduced generation of alkyl radicals from various alkylating agents is the key point to the success of these reactions. This review will summarise advances in this area with emphasis on the reaction mechanisms.

Here we describe a straightforward and efficient approach for regiospecific introduction of an allyl group into cycloalkanol molecules employing a visible-light-mediated ring-opening strategy. A wide range of distally allylated or formylated ketones is furnished from 1-aryl cycloalkanol precursors of variable ring sizes, providing a concise and practical access for the modification of complex natural products. Preliminary mechanistic studies demonstrate that the key O-centered radicals mediate the sequential ring cleavage and allylation/formylation.

A visible-light-induced denitrogenative phosphorylation of benzotriazoles is presented, in which diverse substituted aryl phosphonates could be obtained in good to excellent yields. This efficient protocol exhibits good tolerance with various functional groups. Furthermore, the utility of this photochemical protocol is demonstrated by a gram-scale reaction, and a reasonable mechanism is proposed.

The employment of nitrogen sources with free N-H bonds for amination is considered to be most straightforward and desirable, especially when the C-N bonds are prepared from N-H bonds and non-functionalized carbon sources, such as C-H bonds and C-C double/triple bonds, since this obviates the needs for the pre-installation of reactive groups in the starting materials and leads to a high atom and step economy. Recently, radical chemistry has been resuscitated owing to its great value in organic synthesis, and notable advances have been made in the direct use of N-H bonds for radical-based C-N bond formation with photo-/electrotechniques. Apart from the well-studied N-radical species addition pathway, radical-mediated aminations also proceed through N-atom nucleophilic addition, C-/N-radical cross-coupling, and a hydrogen-atom transfer (HAT) process. This review highlights the recent advances in this area with emphasis on the related reaction mechanisms.

The development of photoredox reactions of 1,3-dipolar cycloaddition of nitrones with alkenes is reported. It offers an efficient synthetic method to obtain isoxazolidine derivatives under mild conditions in synthetically useful yields. The nitrones are cyclized with oxidizable styrenes and aliphatic alkenes via a polar radical crossover cycloaddition reaction through photocatalytic reaction without additives. In addition, bis(indole)methanes can also be prepared through this method.

The photolysis of substituted o-divinylbenzenes promotes a one-step and metal-free conversion to oxatricycles at room temperature. Irradiation o-divinylbenzenes results in an pericyclic reaction to form cyclic o-quinodiemthane intermediates, which subsequently undergo intramolecular oxa-[4+2] cycloaddition to form oxacyclic derivatives.

A mild, metal-free, and absolutely para-selective bromination of aniline derivatives has been developed in excellent yields, wherein the organic dye Eosin Y is employed as the bromine source in company with Selectfluor. Neither air nor moisture sensitive, this facile reaction proceeds smoothly at room temperature and completes within a short time. Mechanistic studies indicate a radical pathway; therefore, the existence of an in situ generated brominating reagent, "Selectbrom", is postulated, which may reasonably account for the unique regioselectivity for the para-bromination of N-acyl- as well as N-sulfonylanilines.

The first visible-light-mediated radical-radical cross-coupling strategy that enables the direct arylation of carbonyl/iminyl derivatives in the presence of Et 3 N has been realized. Such an atom-economical protocol furnishes a broad scope of arylation products such as secondary/tertiary alcohols and amines via a PCET process that facilitates the challenging reduction of C═X (X = O, N). Mechanistic investigation indicates two photocatalytic redox cycles were involved in the process, and Et 3 N was proved to serve as a dual reductant and proton donor. Moreover, the isolated byproducts and controlled experiments could be considered as powerful supporting evidence for our hypothesis.

A novel and efficient method for the synthesis of highly substituted benzobicyclo[2.2.2]octane skeletons has been explored. Under UV-light irradiation, o-divinylbenzenes underwent a pericyclic reaction to form the cyclic o-quinodimethane intermediates which were subsequently reacted with olefins through [4+2] addition to construct the benzobicyclo[2.2.2]octane skeletons in mild conditions. Gram scale reactions demonstrated the synthetic potential application of this protocol.

In moist chloroform solution, the ultraviolet light irradiation would cause N-salicylidene-3-aminopyridine (L) to hydrolyze into salicylaldehyde and 3-aminopyridine. To consider an optical signal (UV light) and a chemical signal (Zn(2+)) as inputs, the luminescence signals as outputs, the logic behavior of compound L was investigated. Interestingly, excited by two different wavelengths lights, two sharp distinct fluorescent spectra were collected. Consequently, a fluorescent 1:2 demultiplexer and a fluorescent half-subtractor were respectively expressed., (Copyright © 2013 Elsevier B.V. All rights reserved.)

An N-salicylidenaniline (SA), compound 1 with 15-crown-5 moiety, was synthesized. The time-dependent NMR was used to track its photochromic process. The experimental results showed that ultraviolet irradiation would lead compound 1 to decompose into the corresponding salicylaldehyde and amine in chloroform solution, instead of experiencing a photochromic process. By the same method, the reported photochromic results of other SAs were also corrected., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In the title compound, C(20)H(19)O(4)P, the dihedral angle between the phenyl rings is 73.3 (4)° and the dihedral angles between the benzene ring and the two phenyl rings are 43.0 (3) and 54.3 (1)°. In the crystal, O-H⋯O hydrogen bonds and weak O-H⋯O inter-actions are observed, which form a supra-molecular sheet parallel to (010).

The ionic chiral auxiliary approach to asymmetric photochemical synthesis discovered by the Scheffer group has been successfully applied to many reactions in the solid state. Enantiomeric excesses of up to 99% were obtained using this method. After a brief introduction of absolute asymmetric synthesis, chirally modified zeolites and host-guest assemblies in asymmetric photochemistry, the bulk of this review will summarize and discuss the application of the solid state ionic chiral auxiliary technique to the Norrish type II reaction, the di-pi-methane photorearrangement, and to a novel retro-Claisen photorearrangement.

The title compound, [Cu(2)V(4)O(12)(C(10)H(8)N(2))(2)](n), shows a two-dimensional copper-vanadate layer composed of eight-membered rings, each containing four corner-sharing VO(4) tetra-hedra; these are linked through six penta-coordinated Cu(II) atoms with the 2,2'-bipyridine ligands attached and pointing above and below the plane of the layer. The Cu atom is coordinated by two N donors from the 2,2'-bipyridine ligand and three O atoms from three adjacent VO(4) units to form a distorted tetragonal pyramid. These layers are further connected by π-π inter-actions between inter-leaving bipyridine ligands of adjacent layers [centroid-centroid distances = 3.63 (1) and 3.68 (1) Å] into a three-dimensional supra-molecular structure.

Solution-phase irradiation of a series of syn-7-benzoylnorbornene derivatives is shown to lead to cis-fused dihydrofuran derivatives in low quantum but excellent chemical yields in what is formally a retro-Claisen rearrangement. In analogy to the well-known Paterno-Buchi reaction, the first step of the rearrangement is suggested to involve (n,pi)(3)-mediated addition of the carbonyl oxygen to the norbornene double bond, producing a triplet 1,4-biradical. This intermediate, rather than closing to the oxetane, undergoes cleavage accompanied by intersystem crossing to form the dihydrofuran. To determine whether the retro-Claisen photorearrangement could be carried out enantioselectively, the 7-benzoylnorbornene reactant was equipped with a para-carboxylic acid substituent to which a series of optically pure amines was attached ionically via salt bridges. Irradiation of these salts in the crystalline state followed by diazomethane workup (the solid-state ionic chiral auxiliary method) was shown to afford the corresponding dihydrofuran in optical yields as high as 93% at 95% conversion. X-ray crystallography revealed that the enantioselectivity arises from crystallization of the reactant in a conformation in which the carbonyl oxygen is more favorably oriented for bond formation to one end of the norbornene double bond than the other, thus leading to a predominance of a single enantiomer.

Structure-reactivity correlations for triplet 1,4-hydroxybiradicals in solution are made difficult by the presence of multiple reactive conformers and the possibility of conformation-dependent intersystem crossing. These problems can be overcome by working in the crystalline state, where the conformations of the 1,4-hydroxybiradicals are fixed and determinable by X-ray crystallography of the parent ketones, assuming that hydrogen atom abstraction occurs with little or no change in conformation. This approach is applied to 15 bi- and tricyclic ketones designed to have slightly different biradical conformations, so that the effect of small and incremental changes in geometry on biradical behavior can be tested. The results indicate that, while geometry does have a strong influence on 1,4-hydroxybiradical partitioning between cyclization, cleavage, and reverse hydrogen transfer, a full understanding of the results requires that the strain involved in forming the cyclization products be taken into account.