Selective Three-Component 1,2-Aminoalkoxylation of 1-Aryl-1,3-dienes by Dual Photoredox and Copper Catalysis

Visible-Light-Accelerated Decarboxylative N-Allylation of γ-Methylidene-δ-valerolactones via Synergistic Pd(0)/Cu(II)/Riboflavin Catalysis

We report a visible-light-accelerated decarboxylative N-allylation of methylidene-δ-valerolactones via synergistic Pd(0)/Cu(II)/riboflavin catalysis. This method enables efficient coupling of diverse anilines and lactones under mild conditions, achieving an up to 93% yield.

Copper-Catalyzed Regioselective 1,4-Sulfonyl Indolylation of 1,3-Dienes with Sulfonyl Chloride and Indoles

A copper-based catalytic system has been described to enable the efficient 1,4-sulfonylindolylation of 1,3-dienes with sulfonyl chloride and indoles. This protocol offers a practical method for the synthesis of allylsulfone-containing indole derivatives with a broad range of compatible functionalities and excellent chemo- and regioselectivities. Mechanistic studies suggest that the copper catalyst plays the dual role of initiating sulfonyl radicals and prompting indole coupling in this conjugated diene-selective 1,4-difunctionalization strategy.

Photoredox-Catalyzed Three-Component Sulfonaminoalkynylation of Alkenes via a Radial/Polar Crossover

We report a photoredox-catalyzed three-component sulfonaminoalkynylation of alkenes with N-aminopyridine salts and potassium alkynyltrifluoroborate salts. This aminoalkylation reaction underwent a radial/polar crossover mechanism, which was distinguished from the previous reports. A variety of β-alkynylated sulfonamides were obtained in moderate to excellent yields. The versatility of this method was further evidenced by its successful application in modifying biological molecules in advanced stages of development.

Photoredox-Catalyzed Aminolactonization of 2-Styrylbenzoic Acids with N-Aminopyridinium Salts to Access 4-Sulfonamino-3,4-dihydroisocoumarins

A photoredox-catalyzed aminolactonization of unsaturated carboxylic acids was achieved using N-aminopyridinium salts as the amino radical precursor. The transformation features mild conditions and a remarkably broad substrate scope, offering an efficient approach to construct a wide range of 4-sulfonamino 3,4-dihydroisocoumarins. Mechanistic studies indicate that the reaction proceeds via a distinctive N-aminopyridinium salt-promoted electrophilic amination of 2-styrylbenzoic acids.

Indium Mediated Reformatsky-Type Allylation of N-tert-Butanesulfinyl Iminoester with 1,3-Butadiene

This study presents the indium-mediated three-component radical Reformatsky-type allylation of N-tert-butanesulfinyl iminoester with 1,3-butadiene. This novel approach offers a rapid synthesis pathway to valuable homoallylic noncanonical amino acids, demonstrated with over 30 examples showing nice regio- and diastereoselectivity. Mechanism studies revealed that allylindium complexes served as key intermediates, formed through a single-electron reduction of allylic radicals by Indium species.

Defluorinative Haloalkylation of Unactivated Alkenes Enabled by Dual Photoredox and Copper Catalysis

A three-component defluorinative haloalkylation of alkenes with trifluoromethyl compounds and TBAX (X = Cl, Br) via dual photoredox/copper catalysis is reported. The mild conditions are compatible with a wide array of activated trifluoromethyl aromatics bearing diverse substituents, and various nonactivated terminal and internal alkenes, enabling straightforward access to synthetically valuable γ-gem-difluoroalkyl halides with high efficiency. Mechanistic studies indicate that the [Cu] complexes not only serve as XAT catalysts but also facilitate the SET reduction of trifluoromethyl groups by photocatalysts. Additionally, the resulting alkyl halide products can serve as versatile conversion intermediates for the synthesis of a diverse range of γ-gem-difluoroalkyl compounds.

Photoinduced Copper-Catalyzed Asymmetric Three-Component Radical 1,2-Azidooxygenation of 1,3-Dienes

Radical-involved multicomponent difunctionalization of 1,3-dienes has recently emerged as a promising strategy for rapid synthesis of valuable allylic compounds in one-pot operation. However, the expansion of radical scope and enantiocontrol remain two major challenges. Herein, we describe an unprecedented photoinduced copper-catalyzed highly enantioselective three-component radical 1,2-azidooxygenation of 1,3-dienes with readily available azidobenziodazolone reagent and carboxylic acids. This mild protocol exhibits a broad substrate scope, high functional group tolerance, and exceptional control over chemo-, regio- and enantioselectivity, providing practical access to diverse valuable azidated chiral allylic esters. Mechanistic studies imply that the chiral copper complex is implicated as a bifunctional catalyst in both the photoredox catalyzed azidyl radical generation and enantioselective radical C-O cross-coupling.

Recent advances in C(sp3)-N bond formation via metallaphoto-redox catalysis

The C(sp3)-N bond is ubiquitous in natural products, pharmaceuticals, biologically active molecules and functional materials. Consequently, the development of practical and efficient methods for C(sp3)-N bond formation has attracted more and more attention. Compared to the conventional ionic pathway-based thermal methods, photochemical processes that proceed through radical mechanisms by merging photoredox and transition-metal catalyses have emerged as powerful and alternative tools for C(sp3)-N bond formation. In this review, recent advances in the burgeoning field of C(sp3)-N bond formation via metallaphotoredox catalysis have been highlighted. The contents of this review are categorized according to the transition metals used (copper, nickel, cobalt, palladium, and iron) together with photocatalysis. Emphasis is placed on methodology achievements and mechanistic insight, aiming to inspire chemists to invent more efficient radical-involved C(sp3)-N bond-forming reactions.

Copper-Catalyzed 1,2-Sulfonyletherification of 1,3-Dienes

A selective three-component 1,2-sulfonyl etherification of aryl 1,3-dienes enabled by copper catalysis to afford biologically interesting alkenyl 1,2-sulfone ether derivatives through C-S and C-O bond formation is described. The protocol proceeds with the sulfonyl chloride and alcohols under simple, mild, and base-free conditions, providing a straightforward route to sulfonylated allyl ether compounds with broad functional group tolerance and excellent chemo- and regioselectivity. Mechanistic studies indicate that the selective alkene difunctionalization includes a key copper-mediated single-electron transfer process.

Photoredox-catalyzed unsymmetrical diamination of alkenes for access to vicinal diamines

A photoredox-catalyzed unsymmetrical diamination of alkenes by using N-aminopyridinium salts and nitriles as the amination reagents has been developed. Various vicinal diamines were obtained in moderate to excellent yields under mild reaction conditions. Furthermore, this protocol could be applied in the late-stage modification of pharmaceuticals and natural products. Preliminary mechanistic studies suggested that this methodology may undergo a radical pathway followed by a Ritter-type reaction.

Copper-Catalyzed Selective Three-Component 1,2-Phosphonoazidation of 1,3-Dienes

We report a copper-catalyzed selective 1,2-phosphonoazidation of conjugated dienes. This three-component reaction is achieved by using readily available P(O)-H compounds and bench-stable NaN3. Salient features of this strategy include its mild reaction conditions, broad functional group tolerance, and high chemoselectivity and regioselectivity. Moreover, the compatibility with the late-stage functionalization of drug molecules, the potential for scalable production, and the feasibility of further modifications of the products underscore the practical utility of this protocol in synthetic applications.

Photoredox-Catalyzed Tandem Cyclization of Enaminones with N-Sulfonylaminopyridinium Salts toward the Synthesis of 3-Sulfonaminated Chromones

A photoredox-catalyzed intermolecular tandem sulfonamination/cyclization of enaminones was realized by using N-aminopyridinium salts as the sulfonaminated reagents without transition-metal catalysts or bases. The reaction exhibits a broad scope and good functional group tolerance, good yields, and regioselectivity. Preliminary mechanistic studies support the radical property of the reaction and the involvement of N-centered radical intermediates.

Visible-Light-Mediated Three-Component Decarboxylative Coupling Reactions to Synthesize 1,4-Diol Monoethers

An efficient approach for 1,2-difunctionalization of aromatic olefins and the synthesis of functionalized 1,4-diols monoethers has been established via a photoinduced three-component reaction of an α-alkoxycarboxylic acid, an aromatic olefin, and an aldehyde. The reaction proceeds by photoinduced oxidative decarboxylation of the carboxylic acid followed by the addition of the α-alkoxyalkyl radical to the olefin, one-electron reduction of the addition radical, and the nucleophilic attack of the resulting carbanion to the aldehyde. Besides the convenient one-pot protocol of the three-component reaction, this method offers several other advantages, including good functional group tolerance for the three substrates, gentle reaction conditions, and ease of scaling up. The reaction mechanism has been investigated through free radical trapping experiment and isotope labeling experiments.

Photoinduced copper-catalyzed selective three-component 1,2-amino oxygenation of 1,3-dienes

This study presents a highly effective method for the photoinduced copper-catalyzed 1,2-amino oxygenation of 1,3-dienes. This synthetic strategy involves the dual roles of a single copper catalyst, which can act as a photosensitizer to generate nitrogen radicals and can also react with allyl radicals via single electron transfer (SET) processes. The method produces a range of quaternary carbon-centered allyl carboxylic esters and tertiary ethers with high yields and excellent regioselectivity under mild reaction conditions.

Emerging Trends in Copper-Promoted Radical-Involved C-O Bond Formations

The C-O bond is ubiquitous in biologically active molecules, pharmaceutical agents, and functional materials, thereby making it an important functional group. Consequently, the development of C-O bond-forming reactions using catalytic strategies has become an increasingly important research topic in organic synthesis because more conventional methods involving strong base and acid have many limitations. In contrast to the ionic-pathway-based methods, copper-promoted radical-mediated C-O bond formation is experiencing a surge in research interest owing to a renaissance in free-radical chemistry and photoredox catalysis. This Perspective highlights and appraises state-of-the-art techniques in this burgeoning research field. The contents are organized according to the different reaction types and working models.

Substituent-Controlled Regioselective Photoinduced Cyclization of N-Allylbenzamides with N-Sulfonylaminopyridinium Salts

The annulation reactions of N-allylbenzamides with N-sulfonylaminopyridinium salts were developed under metal-free photoinduced mild conditions. Substituent-controlled sulfonaminoarylation and sulfonaminooxylation of benzamides were realized: N-allylbenzamides lead to benzosultams, while N-(2-phenylallyl)benzamides give sulfonamidylated oxazoline derivatives. Control experiments indicated that those reactions undergo a radical pathway with arylsulfonamidyl radicals as the intermediates. The aryl C-H bond functionalization in arylsulfonamidyl was involved for the first time to give benzosultams.