How to Achieve Hydrogenation/Hydrofunctionalization via Metal Hydride Complexes.

ConspectusMetal hydride (M-H) complexes have garnered widespread attention in the synthesis of fine chemicals, materials, agrochemicals, and pharmaceuticals owing to the remarkable reactivity of the M-H bonds. Specifically, M-H complexes are active intermediates that catalyze hydrogen-transfer reactions, leading to efficient hydrogenation and hydrofunctionalization of C═C/C═X (X = O or N) bonds in unsaturated organic substrates for the formation of new carbon-hydrogen, carbon-carbon, and carbon-heteroatom bonds.Our research group has long studied M-H transformation mechanisms, with significant advancements over the past decade.

Zinc Promoted Cross-Electrophile Sulfonylation to Access Alkyl-Alkyl Sulfones.

The transition metal-catalyzed multi-component cross-electrophile sulfonylation, which incorporates SO as a linker within organic frameworks, has proven to be a powerful, efficient, and cost-effective means of synthesizing challenging alkyl-alkyl sulfones. Transition metal catalysts play a crucial role in this method by transferring electrons from reductants to electrophilic organohalides, thereby causing undesirable side reactions such as homocoupling, protodehalogenation, β-hydride elimination, etc. It is worth noting that tertiary alkyl halides have rarely been demonstrated to be compatible with current methods owing to various undesired side reactions.

Electrochemical Oxidation Enables Radical Dearomative Spiroannulation to 2H-Spiro[benzofuran-3,9'-fluoren]-2-one.

Developing pragmatic strategies for accessing functional benzofuran-2-ones from 3-([1,1'-biphenyl]-2-yl)benzofuran remains an enduring challenge. Herein, we have achieved a highly discriminating electrochemical oxidative dearomative spiroannulation of 3-([1,1'-biphenyl]-2-yl)benzofuran, culminating in the synthesis of 2H-spiro[benzofuran-3,9'-fluoren]-2-one derivatives. By harnessing the electrophilic intermediates of benzofuryl radical cations supported by DFT calculations, we attain exceptional regioselectivity while eliminating the need for stoichiometric oxidants.

Overlooked interaction between redox-mediator and bisphenol-A in permanganate oxidation.

Research efforts on permanganate (Mn(VII)) combined with redox-mediator (RM), have received increasing attention due to their significant performance for bisphenol-A (BPA) removal. However, the mechanisms underpinning BPA degradation remain underexplored. Here we show the overlooked interactions between RM and BPA during permanganate oxidation by introducing an RM-N-hydroxyphthalimide (NHPI).

Enhancing Hydride Transfer in Catalytic Hydrogenation via σ-Electron-Induced Polarization of Imines.

In this study, we investigated the role of aluminum cations in facilitating hydride transfer during the hydrogenation of imines within the context of Noyori-type metal-ligand cooperative catalysis. We propose a novel model involving aluminum cations directly coordinated with imines to induce activation from the lone pair electron site, a phenomenon termed σ-induced activation. The aluminum metal-hydride amidate complex ("HMn-NAl") exhibits a higher ability of hydride transfer in the hydrogenation of imines compared to its lithium counterpart ("HMn-NLi").

Rhodium-Catalyzed Direct ortho-Arylation of Anilines.

An efficient and broadly applicable rhodium-catalyzed direct ortho-arylation of anilines with aryl iodides relying on readily available aminophosphines as traceless directing groups is reported. Its scope and functional group compatibility were both found to be quite broad as a large variety of both aminophosphines and (hetero)aryl iodides, including complex ones, could be utilized. The ortho-arylated anilines could be obtained in high average yields, without any competing diarylation and with full regioselectivity, which constitutes a major step forward compared to other processes.

Catalyst-Controlled Divergent Generations and Transformations of α-Carbonyl Cations from Alkynes.

α-Carbonyl cations are the umpolung forms of the synthetically fundamental α-carbonyl carbanions. They are highly reactive yet rarely studied and utilized species and their precursors were rather limited. Herein, we report the catalyst-controlled divergent generations of α-carbonyl cations from single alkyne functionalities and the interception of them via Wagner-Meerwein rearrangement.

Valve turning towards on-cycle in cobalt-catalyzed Negishi-type cross-coupling.

Ligands and additives are often utilized to stabilize low-valent catalytic metal species experimentally, while their role in suppressing metal deposition has been less studied. Herein, an on-cycle mechanism is reported for CoClbpy catalyzed Negishi-type cross-coupling. A full catalytic cycle of this kind of reaction was elucidated by multiple spectroscopic studies.

Initiator-Activation Strategy-Enabled Organocatalyzed Reversible-Deactivation Radical Polymerization Driven by Light.

Organocatalyzed reversible-deactivation radical polymerizations (RDRPs) are attractive for many applications. Here, we developed photoredox-mediated RDRP by activating (hetero)aryl sulfonyl chloride (ArSO Cl) initiators with pyridines and designing a novel bis(phenothiazine)arene catalyst. The in situ formed sulfonyl pyridinium intermediates effectively promote controlled chain-growth from ArSO Cl, enabling access to various well-defined polymers with high initiation efficiencies and controlled dispersities under mild conditions.

Revised Mechanism of C(sp)-C(sp) Reductive Elimination from Ni(II) with the Assistance of a Z-Type Metalloligand.

Reductive elimination is a key step in Ni-catalyzed cross-couplings. Compared with processes that proceed from Ni(III) or Ni(IV) intermediates, C(sp)-C(sp) reductive eliminations from Ni(II) centers are challenging due to the weak oxidizing ability of Ni(II) species. In this report, we present computational evidence that supports a mechanism in which Zn coordination to the nickel center as a Z-type ligand accelerates reductive elimination.

How Strain-Release Determines Chemoselectivity: A Mechanistic Study of Rhodium-Catalyzed Bicyclo[1.1.0]butane Activation.

Bicyclo[1.1.0]butane (BCB) derivatives are versatile coupling partners, and various reaction modes for their activation and transformation have been proposed.

Palladium-Catalyzed Intermolecular Asymmetric Dearomative Annulation of Phenols with Vinyl Cyclopropanes.

Herein, we report the Pd(0)-catalyzed intermolecular asymmetric dearomative [3 + 2] annulation of phenols with vinyl cyclopropanes via in situ generated -quinone methide intermediates. A series of highly functionalized spiro-[5,6] bicycles which bear three contiguous stereogenic centers including one all-carbon quaternary were obtained with excellent stereoselectivities. Density functional theory (DFT) calculations indicate that the reactions were controlled by thermodynamics.

Regiospecific construction of -alkenyl benzaldehyde from -bromoenal and vinyl borate.

Herein, we report a Pd-catalyzed regiospecific cycloaromatization of -bromoenal and vinyl borate esters to synthesize -alkenyl substituted benzaldehydes. This allows the construction of complex molecules from simple materials, which may be useful in the search for new optical materials.

Oxymetalation or oxidative cyclization? mechanism of Pd-catalyzed annulation of enynones.

Enynones are powerful synthons for constructing furan derivatives in the presence of transition metal catalysts. Unlike the conventional intramolecular nucleophilic attack with the activation of coinage metals, we propose that enynones undergo an oxidative cyclization process with a Pd(0) species. The full catalytic cycle involves oxidative cyclization, isocyanide insertion, and reductive elimination, which was supported by DFT calculations.

Role of TEMPO in Enhancing Permanganate Oxidation toward Organic Contaminants.

Permanganate (Mn(VII)) has been widely applied as an oxidant in water treatment plants. However, compared with ozone, Fenton, and other advanced oxidation processes, the reaction rates of some trace organic contaminants (TrOCs) with Mn(VII) are relatively low. Therefore, further studies on the strategies for enhancing the oxidation of organic contaminants by Mn(VII) are valuable.

How Solvents Control the Chemoselectivity in Rh-Catalyzed Defluorinated [4 + 1] Annulation.

Density functional theory calculations have been performed to reveal the chemoselectivity of Rh-catalyzed chiral C-F cleavage and γ-site functionalization. We found that the chemoselectivity is controlled by β-F elimination in methanol solvent, leading to formation of the alkynylic product. In isobutyronitrile solvent, the chemoselectivity is controlled by the allene insertion step, where the fluoroalkenylic product can be observed.

Nickel-Catalyzed C-F/N-H Annulation of Aromatic Amides with Alkynes: Activation of C-F Bonds under Mild Reaction Conditions.

The Ni-catalyzed reaction of -fluoro-substituted aromatic amides with alkynes results in C-F/N-H annulation to give 1(2)-isoquinolinones. A key to the success of the reaction is the use of KOBu or even weak base, such as CsCO. The reaction proceeds in the absence of a ligand and under mild reaction conditions (40-60 °C).

Layered Chirality Relay Model in Rh(I)-Mediated Enantioselective C-Si Bond Activation: A Theoretical Study.

A three-layer chirality relay model is proposed for Rh(I)-mediated enantioselective siletane activation. A chiral ligand in the back layer controls the position of the alkyne-coordinated metal center in the middle layer, which then provides a chiral environment for the incoming substrate at the front layer. A two-dimensional contour map analysis further clarified this model.

Reaction scope and mechanistic insights of nickel-catalyzed migratory Suzuki-Miyaura cross-coupling.

Cross-coupling reactions have developed into powerful approaches for carbon-carbon bond formation. In this work, a Ni-catalyzed migratory Suzuki-Miyaura cross-coupling featuring high benzylic or allylic selectivity has been developed. With this method, unactivated alkyl electrophiles and aryl or vinyl boronic acids can be efficiently transferred to diarylalkane or allylbenzene derivatives under mild conditions.

Enhanced Transformation of Emerging Contaminants by Permanganate in the Presence of Redox Mediators.

In this study, a permanganate/redox mediator system for enhanced transformation of a series of emerging contaminants was evaluated. The presence of various redox mediators (i.e.

Hydrogen-Bond-Induced Chiral Axis Construction: Theoretical Study of Cinchonine-Thiourea-Catalyzed Enantioselective Intramolecular Cycloaddition.

Theoretical calculations were performed to investigate the mechanism and enantioselectivity of cinchonine-thiourea-catalyzed intramolecular hetero-Diels-Alder cycloaddition of ethynylphenol derivatives to afford axial chirality naphthalenylpyran products via a vinylidene ortho-quinone methide (VQM) intermediate. The results show that this transformation occurs through a reaction pathway involving the deprotonation of the naphthol moiety by the quinuclidine base, intramolecular proton transfer in ammonium naphthalenolate, and [4+2] cycloaddition. It is found that the axial chirality of the VQM intermediate is generated by the protonation step, which affects the enantioselectivity of the reaction.

Mechanism of Brønsted-Base-Mediated Borylation of Propynols: A DFT Study.

DFT calculations are used to reveal the mechanism of Brønsted-base-mediated borylation of propynols. The reaction is predicted to go through a key intermediate of alkenylboronate. Therefore, the possible pathways involve two key steps, borylation and reductive dehydroxylation.

Role of Alkaline-Earth Metal-Catalyst: A Theoretical Study of Pyridines Hydroboration.

Density functional theory (DFT) calculations have been performed to investigate the mechanism of alkaline-earth-metal-catalyzed hydroboration of pyridines with borane. In this reaction, the active catalytic species is considered to be an alkaline earth metal hydride complex when the corresponding alkaline earth metal is used as the catalyst. The theoretical results reveal that initiation of the catalytic cycle is hydride transfer to generate a magnesium hydride complex when β-diimine alkylmagnesium is used as a pre-catalyst.

Theoretical Study of the Addition of Cu-Carbenes to Acetylenes to Form Chiral Allenes.

Terminal alkynes have become one of the most versatile building blocks for C-C bond construction in the past few decades, and they are usually considered to convert to acetylides before further transformations. In this study, a novel direct nucleophilic addition mode for Cu(I)-catalyzed cross-coupling of terminal alkynes and N-tosylhydrazones to synthesize chiral allenes is proposed, and it was investigated by density functional theory with the M11-L density functional. Three different reaction pathways were considered and investigated.

Theoretical Study of Ni-Catalyzed C-N Radical-Radical Cross-Coupling.

A computational study was carried out to investigate the mechanism and the origin of chemoselectivity in nickel-catalyzed C-N radical-radical cross-coupling reaction. The global electrophilicity index ω° and global nucleophilicity index N° were used to quantitatively describe the electrophilic or nucleophilic character of the carbon radical, nitrogen radical, and Ni(II) complex. The calculated ω° and N° values indicate that introduction of nickel makes C-N cross-coupling to be a facile process.