Photocatalytic Modular Cyanoalkylamination of Alkenes Involving Two Different Iminyl Radicals

Development of an Easy-To-Handle Redox Active Group for Alcohols: Catalytic Transformation of Tertiary Alcohols to Nitriles

The generation of radical intermediates via SET-mediated deoxygenation of activated alcohol derivatives is desirable, as alcohols can be utilized in various radical-mediated reactions. Herein, we introduce α-N-phthalimido-oxy isobutyrate (NPIB) as a novel activating group for alcohols. Essentially, it is a more chemically robust alternative to Overman's N-phthalimidoyl oxalate group. The utility of the NPIB group is showcased in the conversion of tertiary alcohols to nitriles under Ir/Cu dual catalysts and in the presence of TMSCN upon blue LED irradiation. With our newly developed NPIB handle, the reactivities of N-hydroxyphthalimide esters derived from carboxylic acids would be achievable with naturally and commercially more abundant alcohol substrates.

Construction of C-P Bonds from Free Cyclobutanone Oximes and Chlorophosphines via Radical-Radical Coupling

Herein, we report a catalyst-free reaction of cyclobutanone oximes with chlorophosphines (R2PCl), which forms a fragile C═N-O-PR2 species that undergoes N-O homolysis, fragmentation, and radical-radical coupling, leading to the formation of cyano-containing phosphine oxides in good yields. The reaction features an in situ activation of cyclobutanone oximes for radical generation, in which R2PCl plays a dual role as both an activator and a reactant.

Photocatalytic Unsymmetrical Diamination of Styrenes, Indoles, and Benzofurans Facilitated by Benzotriazolyl and Iminyl Radicals

Utilizing energy transfer catalysis, this research employed the bifunctional reagents benzotriazole carboxylic acid oxime esters to simultaneously generate benzotriazole and imine radicals. The synthesis of two distinct C-N bonds in a single conversion is showcased through radical addition and radical-radical cross-coupling processes between benzotriazole carboxylic acid oxime ester and olefins. This process facilitates the intermolecular two-component unsymmetrical diamination reaction of olefins. Using this approach, more than 40 benzotriazole-containing molecules were successfully synthesized using styrene, indole, and benzofuran as acceptors, with yields ranging from moderate to excellent.

Dual Oxidation of Epoxides with a High-Valent Cu(III)-CF3 Compound and DMSO to Access 1,2-Diketones

This study reports sequential dehydrogenation and transfer oxygenation of 1,2-diarylepoxides by high-valent phenCu(III)(CF3)3 and DMSO to produce 1,2-diketones. The Cu(III)-CF3 compound serves as a CF3 radical source to abstract the hydrogen atom of the epoxide ring. The resulting ether α-carbon radical undergoes ring-opening rearrangement to give a ketone α-carbon radical intermediate, which is oxygenated by DMSO with the release of Me2S. The combination of a Cu(III)-CF3 compound and DMSO may be exploited to develop other novel oxidation reactions.

Photoredox/Nickel Dual Catalysis-Enabled Cross-Dehydrogenative C-H Amination of Indoles with Unactivated Amine

Herein, a direct cross-dehydrogenative C-H amination of indoles has been successfully achieved, enabled by the merger of photocatalysis with nickel catalysis. This developed process does not require stoichiometric oxidants and prefunctionalization of amine partners, providing a concise platform for C-N bond formation. Moreover, the synthetic practicality of this transformation was well revealed by its high step- and atom-economy, high reaction efficiency, and broad functional group tolerance.

The Merger of Halogen Atom Transfer (XAT) and Energy Transfer Catalysis (EnT) for the Modular 1,2-Iminylalkylation of Diazenes

The 1,2-iminylalkylation of diazenes using alkyl iodides in combination with an O-benzoyl oxime is reported. In this transformation, O-benzoyl oxime acted as a radical precursor and XAT mediator. In addition to common alkyl iodides, other alkyl iodides such as iodomethane, iodomethane-d3, trifluoroiodomethane, ethyl difluoroiodoacetate, and iodoalkanes containing unprotected hydroxyl and amide groups can also serve as C-radical precursors in the 1,2-iminylalkylation with electrophilic diazenes as radical acceptors.

Photoinduced Difunctionalization of Diazenes Enabled by N-N Radical Coupling

In this study, a metal-free difunctionalization strategy for diazenes was developed using a range of bifunctionalization reagents. This strategy involves a unique N(sp3)-N(sp2) radical coupling between the hydrazine radical and the imine radical. More than 30 triazane core motifs were constructed by installing imines and various functional groups, including alkyl, phenyl, cyanoalkyl, and sulfonyl groups, on both ends of the nitrogen-nitrogen bond of diazenes in an efficient manner.

Photocatalytic Multicomponent 1,n-Carboimination with Alkyl Iodides and O-Benzoyl Oxime through EnT and XAT Processes

In this study, we developed a strategy using commercially available alkyl iodides and O-benzoyl oxime to efficiently introduce alkyl and iminyl groups via energy transfer and halogen-atom transfer processes. We performed three-component 1,2-carboimination of olefins and four-component 1,4-carboimination across olefins and alkynes, resulting in the synthesis of over 60 nitrogen-containing molecules. Moreover, this transformation enables the synthesis of molecules with sensitive groups that were previously difficult to achieve.

EnT-Mediated Amino-Sulfonylation of Alkenes with Bifunctional Sulfonamides: Access to β-Amino Sulfone Derivatives

β-Amino sulfones are commonly found structural motifs in biologically active compounds. Herein, we report a direct photocatalyzed amino-sulfonylation reaction of alkenes for the efficicient production of important compounds by simple hydrolysis without the need for additional oxidants and reductants. In this transformation, the sulfonamides worked as bifunctional reagents, simultaneously generating sulfonyl radicals and N-centered radicals which were added to alkene in a highly atom-economical fashion with high regioselectivity and diastereoselectivity. This approach showed high functional group tolerance and compatibility, facilitating the late-stage modification of some bioactive alkenes and sulfonamide molecules, thereby expanding the biologically relevant chemical space. Scaling up this reaction led to an efficient green synthesis of apremilast, one of the best-selling pharmceuticals, demonstrating the synthetic utility of the applied method. Moreover, mechanistic investigations suggest that an energy transfer (EnT) process was in operation.

Visible-Light-Induced Radical Cascade Cross-Coupling via C(sp3)-H Activation and C-N/N-O Cleavage: Feasible Access to Methylenebisamide Derivatives

Here we report facile and manipulable access to methylenebisamide derivatives via visible-light-driven radical cascade processes incorporating C(sp³)-H activation and C-N/N-O cleavage. Mechanistic studies reveal that a traditional Ir-catalyzed photoredox pathway and a novel copper-induced complex-photolysis pathway are both involved, contributing to activating the inert N-methoxyamides and rendering the valuable bisamides. This approach exhibits many advantages, including mild reaction conditions, broad scope and functional group tolerance, and competitive step economy. Given the mechanistic plenitude and operational simplicity, we believe this package deal paves a promising way for the synthesis of valuable nitrogen-containing molecules.

Photochemical Alkene Trifluoromethylimination Enabled by Trifluoromethylsulfonylamide as a Bifunctional Reagent

Herein, we disclose a facile and versatile trifluoromethylimination of alkene with a rationally designed N-(diphenylmethylene)-1,1,1-trifluoromethanesulfonamide as a bench-stable and readily accessible carboamination reagent. Enabled by an energy transfer (EnT) process, an array of alkenes were able to be facilely CF₃-iminated under metal-free photocatalytic conditions. The mild reaction conditions and good functional group compatibility render this protocol highly valuable for the difunctionalization of olefins with structural complexity and diversity.

Photocatalytic 1,2-Iminosulfonylation and Remote 1,6-Iminosulfonylation of Olefins

A new class of iminosulfonylation reagents were developed and extensively used in the 1,2-iminosulfonylation of various olefins. Olefins containing bioactive molecules, such as indomethacin, gemfibrozil, clofibrate, and fenbufen, afforded the desired iminosulfonylation products in synthetically useful yields. Furthermore, the first remote 1,6-iminosulfonylation of alkenes was realized by using oxime ester bifunctionalization reagents. Overall, more than 40 structurally diverse β-imine sulfones were obtained in moderate to excellent yields.

Photosensitized Vicinal Sulfonylamination of Alkenes with Oxime Ester and DABCO·(SO2)2

A metal-free photosensitized three-component reaction of oxime esters, alkenes, and DABCO·(SO₂)₂ was developed. This protocol could accommodate a wide substrate scope, including activated and unactivated alkenes and aryl and aliphatic carboxylic acid oxime esters, delivering a broad range of β-amino sulfones in moderate to high yields. The insertion of SO₂ as a linker moiety allows the manipulation of the functionality in the reaction process, expanding the utility of oxime esters as bifunctional reagents.

Photoinduced Remote C(sp3)-H Imination Enabled by Vinyl Radical-Mediated 1,5-Hydrogen Atom Transfer

A vinyl radical-mediated 1,5-hydrogen atom transfer strategy for remote C(sp³)-H imination under visible-light-induced photochemical metal-free conditions afforded diverse γ-imino alkenes with excellent stereoselectivity. Oxime ester-based bifunctional reagents provided not only nucleophilic alkyl radicals for radical addition reactions with electron-deficient alkynes but also long-lived steady-state imine radicals for trapping alkyl radicals following the intramolecular 1,5-hydrogen migration of unstable olefin radicals.