Organocatalytic Asymmetric Synthesis of o-Carboranyl Amines

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Янв. 14, 2025

Carboranyl amines are distinct from typical organic amines. Due to the electronic influence of carborane cage, they have low nucleophilicity and reluctant alkylate. Moreover, asymmetric synthesis chiral carboranes is still in its infancy. Herein we achieved first catalytic N-alkylation o-carboranyl amine, providing general access diverse secondary with high efficiency enantioselectivity under mild conditions. For time, organocatalysis was introduced chemistry. Key success use situ generated (naphtho-)quinone methides as alkylating reagents suitable acid catalysts. This protocol also applicable S-alkylation 1-SH-o-C2B10H11. Control experiments kinetic studies provided important insights into reaction mechanism, which likely involves rate-determining generation quinone methide followed by fast enantio-determining nucleophilic addition.

Язык: Английский

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Palladium-Catalyzed Regioselective B(9)-Amination of o-Carboranes and m-Carboranes in HFIP with Broad Nitrogen Sources

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(18), С. 8371 - 8378

Опубликована: Май 2, 2022

Amination of carboranes has a good application prospect in organic and pharmaceutical synthesis. However, the current methods used for this transformation suffer from limitations. Herein, we report practical method highly regioselective formation B-N bond by Pd(II)-catalyzed B(9)-H amination o- m-carboranes hexafluoroisopropanol (HFIP) with different nitrogen sources under air atmosphere. The silver salt HFIP solvent play critical roles present protocol. mechanistic study reveals that acts as Lewis acid to promote electrophilic palladation step forming heterobimetallic active catalyst PdAg(OAc)3; strong hydrogen-bond-donating ability low nucleophilicity enhance Pd(II). It is believed these N-containing are potentially great importance synthesis new pharmaceuticals.

Язык: Английский

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Facile Construction of New Hybrid Conjugation via Boron Cage Extension

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(6), С. 3577 - 3587

Опубликована: Фев. 6, 2023

Aromatic polycyclic systems have been extensively utilized as structural subunits for the preparation of various functional molecules. Currently, aromatics-based are predominantly generated from extension two-dimensional (2D) aromatic rings. In contrast, compounds based on three-dimensional (3D) aromatics such boron clusters less studied. Here, we report three types cluster-cored tricyclic molecular systems, which constructed a 2D ring, 3D nido-carborane, and an alkyne. These new can be facilely accessed by Pd-catalyzed B-H activation subsequent cascade heteroannulation carborane pyridine with alkyne in isolated yield up to 85% under mild conditions without any additives. Computational results indicate that newly ring fusion carborane, pyridyl is non-aromatic. However, not only leads 1H chemical shift considerably downfield shifted owing strong diatropic current embedded but also devotes new/improved physicochemical properties including increased thermal stability, emergence absorption band, largely red-shifted emission band enhanced efficiency. Besides, number bright, color-tunable solid emitters spanning over all visible light obtained absolute luminescence efficiency 61%, contrast aggregation-caused quenching of, e.g., Rhodamine B containing 2D-aromatics-fused structure. This work demonstrates hybrid conjugated might promising scaffolds construction

Язык: Английский

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Direct B–H Functionalization of Icosahedral Carboranes via Hydrogen Atom Transfer

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(13), С. 7638 - 7647

Опубликована: Март 22, 2023

The efficient and selective functionalization of icosahedral carboranes (C2B10H12) at the boron vertexes is a long-standing challenge owing to presence 10 inert B-H bonds in similar chemical environment. Herein, we report new reaction paradigm for direct via homolysis enabled by nitrogen-centered radical-mediated hydrogen atom transfer (HAT) strategy. Both HAT process carborane bond resulting boron-centered carboranyl radical intermediate have been confirmed experimentally. occurs most electron-rich vertex with lowest dissociation energy (BDE). Using this strategy, diverse derivatization, including thiolation, selenation, alkynylation, alkenylation, cyanation, halogenation, achieved satisfactory yields under photoinitiated condition metal-free redox-neutral fashion. Moreover, synthetic utility current protocol was also demonstrated both scale-up construction carborane-based functional molecules. Therefore, methodology opens pathway functionalization, which distinct from heterolytic mechanism traditional strategies.

Язык: Английский

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B(9)-OH-o-Carboranes: Synthesis, Mechanism, and Property Exploration

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(13), С. 7331 - 7342

Опубликована: Март 24, 2023

Herein, we present a chemically robust and efficient synthesis route for B(9)-OH-o-carboranes by the oxidation of o-carboranes with commercially available 68% HNO3 under assistance trifluoromethanesulfonic acid (HOTf) hexafluoroisopropanol (HFIP). The reaction is highly wide scope carboranes, selectivity B(9)/B(8) up to 98:2. success this transformation relies on strong electrophilicity oxidizability HNO3, promoted through hydrogen bonds Brønsted HOTf solvent HFIP. Mechanism studies reveal that o-carborane involves an initial electrophilic attack atom at most electronegative B(9) o-carborane. In transformation, B-H bond nucleophilic site, which different from substitution reaction, where boron site. Therefore, oxidation-reduction mild conditions in N(V) → N(III) H(-I) H(I). derivatization 9-OH-o-carborane was further examined, carboranyl group successfully introduced amino acid, polyethylene glycol, biotin, deoxyuridine, saccharide. Undoubtedly, approach provides selective way rapid incorporation carborane moieties into small molecules application neutron capture therapy, requires targeted delivery boron-rich groups.

Язык: Английский

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Photoinduced Selective B–H Activation of nido-Carboranes

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(11), С. 7791 - 7802

Опубликована: Март 10, 2024

The development of new synthetic methods for B–H bond activation has been an important research area in boron cluster chemistry, which may provide opportunities to broaden the application scope clusters. Herein, we present a reaction strategy direct site-selective functionalization nido-carboranes initiated by photoinduced cage via noncovalent cage···π interaction. As result, nido-carborane radical is generated through single electron transfer from 3D 2D photocatalyst upon irradiation with green light. resulting transient could be directly probed advanced time-resolved EPR technique. In air, subsequent transformations active have led efficient and selective B–N, B–S, B–Se couplings presence N-heterocycles, imines, thioethers, thioamides, selenium ethers. This protocol also facilitates both late-stage modification drugs synthesis nido-carborane-based drug candidates neutron capture therapy (BNCT).

Язык: Английский

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Theoretical study on precise regulation of ESIPT reaction based on ICT effect of o-carborane derivatives

Journal of Molecular Structure, Год журнала: 2024, Номер 1321, С. 139985 - 139985

Опубликована: Сен. 10, 2024

Язык: Английский

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Unraveling aromaticity: the dual worlds of pyrazole, pyrazoline, and 3D carborane

Beilstein Journal of Organic Chemistry, Год журнала: 2025, Номер 21, С. 412 - 420

Опубликована: Фев. 21, 2025

A new series of o -carborane-fused pyrazoles has been recently successfully synthesized. This fusion was expected to create a hybrid 3D/2D aromatic system, combining the 3D aromaticity -carborane with 2D pyrazole. However, while boron cage retains its character, pyrazole’s is lost. As result, rather than forming pyrazoles, synthesis yielded pyrazolines, which are non-aromatic. The limited overlap between π molecular orbitals (MOs) planar heterocycle and n + 1 MOs carborane prevents significant electronic delocalization two fused components. contrasts pyrazole benzene form indazole, where both rings maintain their aromaticity. Our findings demonstrate that peripheral σ-aromaticity π-aromaticity orthogonal, making true system unachievable. highly aromatic, generating negative NICS values (−25 −30 ppm). We have observed these high extend rings, leading incorrect estimations Therefore, relying solely on can be misleading, other computational indicators, along experimental or structural data, should used accurately assess

Язык: Английский

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Visible-Light-Promoted Nickel-Catalyzed Cross-Coupling of Iodocarboranes with (Hetero)Arenes via Boron-Centered Carboranyl Radicals

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(18), С. 7960 - 7965

Опубликована: Апрель 22, 2022

A general strategy for the generation of hypervalent boron-centered carboranyl radicals at B(3), B(4), and B(9) positions has been developed first time via visible-light-promoted iodine atom abstraction from iodo-o-carboranes by low-valent nickel complex. These react with various (hetero)arenes to afford a wide range cage B-arylated carborane derivatives room temperature in very good excellent yields broad substrate scope. Their electrophilicities are dependent on vertex charges follow order B(3) > B(4) B(9). Both visible light catalyst proved critical radicals. The involvement boron is supported control experiments. reaction mechanism associated these reactions also proposed. This offers new protocol selected vertex, leading facile synthesis large class substituted molecules.

Язык: Английский

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Electrochemical Cage Activation of Carboranes

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(20)

Опубликована: Фев. 11, 2022

Abstract Carboranes are boron–carbon molecular clusters that possess unique properties, such as their icosahedron geometry, high boron content, and delocalized three‐dimensional aromaticity. These features render carboranes valuable building blocks for applications in supramolecular design, nanomaterials, optoelectronics, organometallic coordination chemistry, neutron capture therapy (BNCT) agents. Despite tremendous progress this field, stoichiometric chemical redox reagents largely required the oxidative activation of carborane cages. In context, electrosyntheses represent an alternative strategy more sustainable syntheses. It is only recent few years considerable has been made electrochemical cage functionalization carboranes, which summarized Minireview. We anticipate electrocatalysis will serve increasingly powerful stimulus within current renaissance electrochemistry.

Язык: Английский

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