Advanced Synthesis & Catalysis最新文献

A cobalt-catalyzed protocol for diastereo- and enantioselective reductive coupling of unactivated cyclobutenes and aldimines through oxidative cyclization promoted by a chiral bisphosphine–cobalt is presented. Such processes represent an unprecedented reaction pathway for cobalt catalysis that enable umpolung reactivity of cyclobutenes with imines and incorporation of a chiral amino-containing fragment onto the four-membered ring scaffold, delivering a broad scope of enantioenriched cyclobutyl amines in up to 98% yield and >99.5:0.5 er as a single diastereomer. Functionalization provided a variety of densely functionalized cyclobutanes that are otherwise difficult to access. Preliminary mechanistic studies revealed that the reaction proceeded through diastereo- and enantioselective oxidative cyclization followed by protonation. Density functional theory calculations elucidated the origin of stereoselectivity in detail.

Harnessing chlorine radicals (Cl^•) for selective organic transformations has remained challenging due to their extreme reactivity and dependence on unstable chlorine precursors. Here, we present a visible-light strategy that directly generates Cl^• from sodium chloride (NaCl), an abundant, benign, and previously inaccessible chlorine source. Using perylenediimide (PDI) as a sustainable, metal-free photocatalyst and N-fluorobenzenesulfonimide (NFSI) as a radical cargo, chloride anions were oxidized to Cl^•, which drove efficient oxydihalogenation of terminal and internal alkynes. This approach could overcome long-standing solubility and redox barriers, affording gem-dihaloketones in high yields. Mechanistic studies confirmed radical intermediacy and revealed the unprecedented role of NaCl as a chlorine radical progenitor. This work establishes inorganic halide salts as renewable radical precursors and provides a sustainable platform for green halogenation chemistry.

Herein, we have reported an efficient AgSbF₆ catalyzed decarbonylative tandem inverse electron demand hetero Diels–Alder reaction in a very moderate temperature for the construction of quinoline derivatives from 2-(p-tolyl)-1H-inden-1-one with a variety of internal alkynes. To understand the role of the Lewis acid in the reaction, highest occupied molecular orbital-lowest unoccupied molecular orbital gaps are compared for the adducts formed between the diene and AgSbF₆. A mechanistic investigation, utilizing density functional theory calculations, revealed a clear preference for the inverse electron demand hetero Diels–Alder reaction pathway. The release of carbon monoxide gas has been detected through headspace gas chromatography analysis. This strategy enables the one pot synthesis of quinoline derivatives which offer substantial potential in drug discovery.

Accessing alcohols from readily available chemical feedstocks is a critical process within synthetic methodology. The hydration of olefins is a convenient method for the introduction of an alcohol functional group, ideally via the direct addition of water across the alkene. However, current transition metal-catalysed protocols (Mukaiyama-type hydration) are dominated by radical addition to molecular oxygen. Ionic processes involving direct hydration with water are underexplored, yet highly desirable due to the simplicity of the reagents required. Herein, we report a cobalt-salen catalysed hydration of alkenes proceeding via a radical–polar crossover mechanism and subsequent nucleophilic attack of water. This is a complementary protocol to previously reported radical-based hydrations, which display analogous reactivity to traditional acid-catalysed methods. The mild reaction conditions employed make the protocol synthetically practical and convenient for accessing alcohols from the corresponding alkenes.

Regioselective, metal-free, CH chlorination of phenols is challenging. These reactions generally proceed via electrophilic aromatic substitution, resulting in pure 2- or 4-chlorinated products or a mixture of 2- and 4-substituted isomers. However, 3-substitution is electronically forbidden in these cases. Electrophilic aromatic chlorination involves toxic reagents, low tolerance for functional groups, and the generation of waste products from the chlorinating agent. Improvizations involving classical preformed chlorinating agents, oxidative chlorination, and transition metal catalysis, among others, require harsh conditions, high temperatures, directing groups, and low atom economy, despite achieving high selectivity. Few reports have also utilized the activation of arenes to facilitate regioselective nucleophilic chlorination. In a unique progression in phenol chemistry, we report a regioselective, indirect, catalyst- and metal-free synthesis of 2-chlorophenols via the chlorination of quinone monoacetals (QMA), derived from the oxidative dearomatization of phenol, using dimethyl chlorohydrosilane as a chloride source. Further, Brønsted acid-catalyzed chlorination of QMA–MBH adducts afforded regioselective, metal-free, solvent-switchable 3- or 2-chlorophenols via a one-pot cascade reaction. C-2-chlorination proceeds via Michael addition of Cl⁻ ion to the intermediate phenoxonium ion, while C-3 chlorination occurs via Cl⁻ addition to a silane-activated quinone intermediate. This approach is well-suited for late-stage functionalization in pharmaceuticals, natural products, and complex molecules.

We developed a three-component intermolecular alkoxysulfurization or estersulfurization of styrenes for the synthesis of emote alkoxy (ester) substituted thioether derivatives through copper/visible light catalyzed strategy. A variety of substrates were successfully converted into the desired sulfur-containing products in moderate to good yields, demonstrating good functional group tolerance and excellent regioselectivity. Moreover, this method can be readily applied to modify bioactive molecules. A range of substrates, including perillyl alcohol, citronellol, geraniol, L-menthol, and cholesterol, were successfully install to olefins with high selectivity.

The donor–acceptor–donor (DAD) complex model provides a reliable strategy for mediating direct decarboxylative coupling between two electron donors, effectively eliminating the need for amino acid preactivation, external photocatalysts, or transition-metal catalysts. Herein, a metal- and photocatalyst-free direct decarboxylative amination has been developed through photoactive DAD complexes. This strategy enables efficient access to valuable sulfur-containing heterocycles, including key intermediates for NEK2 inhibitors and cumene oxidation inhibitors, under mild blue-light irradiation. Mechanistic studies confirm the formation of a DAD complex, which, upon photoexcitation, undergoes a single-electron transfer (SET) process to generate radical species, followed by decarboxylation and selective CN coupling. The method features broad substrate scope, operational simplicity, and scalability, providing a practical and sustainable alternative to conventional photocatalytic systems.

While high-valent copper intermediates are pivotal for efficient peroxydisulfate (PDS) activation, their generation and role in heterogeneous catalysis remain unclear. Herein, we demonstrate that a nonstoichiometric Cu_0.84Bi_2.08O₄ catalyst enables the dark activation of PDS via a novel pathway dominated by a surface-bound Cu(III)-peroxo intermediate (≡Cu(III)-O−O−SO₃). A suite of spectroscopic and chemical probes revealed that this Cu(III)-peroxo species, along with superoxide radicals (•O₂⁻), acts as the primary oxidant, enabling the highly selective and rapid degradation of bisphenol A (BPA) and other phenolic pollutants. Furthermore, H₂O₂ generated from PDS hydrolysis synergistically participates in the reaction, accounting for the exceptionally high PDS utilization efficiency of the system. The system exhibits remarkable robustness, maintaining high activity over a wide pH range (4–11) and demonstrating strong resistance to interference from ions. This study elucidates a distinct Cu(III)-peroxo-mediated mechanism and offers a new strategy for designing highly selective catalysts for environmental remediation.

Constructing polymer photocatalysts that can concurrently accomplish charge transfer and mass transport to catalytic sites remains a formidable task. In this study, by cross-linking electron-rich polyphenol and electron-poor phenothiazine units, two hydrophilic and porous organic polymer photocatalysts characterized by densely packed donor–acceptor units are deliberately designed. The hydrophilic phenolic hydroxyl group in the donor moiety and the aperture channel neighboring the acceptor unit facilitate the capture of water and oxygen at the catalytic site. Meanwhile, the donor–acceptor columns serve as charge supply chains and numerous water oxidation and oxygen reduction centers. These photocatalysts are used for the photocatalytic synthesis of hydrogen peroxide from water and oxygen without the use of sacrificial reagents. Therein, the polymer containing tetramethyl groups shows high selectivity for the photogeneration of hydrogen peroxide, achieving a yield rate of 691.3 μmol g⁻¹ h⁻¹ (16.73 mM g⁻¹) and an apparent quantum yield (AQY) of 11.9% under 630 nm irradiation. This organic polymer catalyst system exhibits considerable potential as a promising artificial photosynthesis system capable of realizing simultaneous charge transfer and mass transfer.