Stereoselective Synthesis of Trisubstituted Vinylboronates from Ketone Enolates Triggered by 1,3-Metalate Rearrangement of Lithium Enolates.

An unprecedented stereoselective synthesis of trisubstituted vinylboronates is reported to proceed by direct borylation of lithium ketone enolates under transition-metal-free conditions. The stereospecific C-O borylation of lithium enolates was triggered by a carbonyl-induced 1,3-metalate rearrangement via a C-bound boron enolate. DFT calculations and control experiments revealed that the stereoselectivity is controlled by sterics.

Catalytic recycling of NAD(P)H.

A large number of industrially relevant enzymes depend upon dihydronicotinamide adenine dinucleotide (NADH) and dihydronicotinamide adenine dinucleotide phosphate (NADPH) cofactors, which are too expensive to be added in stoichiometric amounts. Existing NAD(P)H-recycling systems suffer from low activity, or the generation of side products. This review focuses on NAD(P)H cofactor regeneration catalyzed by transition metal complexes such as rhodium, ruthenium and iridium complexes using cheap reducing agents such as hydrogen (H) and ethanol, which have attracted increasing attention as sustainable energy carriers.

BuOK-triggered bond formation reactions.

Recently, inexpensive and readily available BuOK has seen widespread use in transition-metal-free reactions. Herein, we report the use of BuOK for S-S, S-Se, N[double bond, length as m-dash]N and C[double bond, length as m-dash]N bond formations, which significantly extends the scope of BuOK in chemical synthesis. Compared with traditional methods, we have realized mild and general methods for disulfide, azobenzenes imine synthesis.

Bioinspired Manganese and Iron Complexes for Enantioselective Oxidation Reactions: Ligand Design, Catalytic Activity, and Beyond.

The development of efficient methods for the enantioselective oxidation of organic molecules continues to be an important goal in organic synthesis; in particular, the use of earth-abundant metal catalysts and environmentally friendly oxidants in catalytic asymmetric oxidation reactions has attracted significant interest over the last several decades. In nature, metalloenzymes catalyze a wide range of oxidation reactions by activating dioxygen under mild conditions. Inspired by selective and efficient oxidation reactions catalyzed by metalloenzymes, researchers have developed a number of synthetic model compounds that mimic the functionality of metalloenzymes.

Precise regulation of the selectivity of supported nano-Pd catalysts using polysiloxane coatings with tunable surface wettability.

A facile method was developed for surface modification of supported nano-Pd catalysts with tailorable wettability. The obtained Pd/TiO2@POS catalytic materials could be used in the controllable synthesis of styrene and ethylbenzene obtained from hydrogenation of phenylacetylene and the selective synthesis of imine and N-methylanilines via a reductive amination reaction. The precise modification of the hydrophilicity/hydrophobicity of the catalyst surface is crucial to realize this targeted transformation.

Recent advances in the borylative transformation of carbonyl and carboxyl compounds.

Organoboron compounds are powerful reagents in synthetic chemistry. Carbonyl and carboxyl compounds are widely accessible chemical feedstocks. The synthesis of organoboron compounds from these basic chemicals is important for chemical synthesis nowadays.

Polyoxometalate-Based Catalysts for CO Conversion.

Polyoxometalates (POMs) are a diverse class of anionic metal-oxo clusters with intriguing chemical and physical properties. Owing to unrivaled versatility and structural variation, POMs have been extensively utilized for catalysis for a plethora of reactions. In this focused review, the applications of POMs as promising catalysts or co-catalysts for CO conversion, including CO photo/electro reduction and CO as a carbonyl source for the carbonylation process are summarized.

Asymmetric Synthesis of Chiral 1,4-Enynes through Organocatalytic Alkenylation of Propargyl Alcohols with Trialkenylboroxines.

A highly enantioselective synthesis of 1,4-enynes is described that proceeds through an organocatalytic reaction between propargyl alcohols and trialkenylboroxines. Our strategy relies on acid-mediated generation of the carbocationic intermediate from propargyl alcohols followed by enantioselective alkenylation with trialkenylboroxines. A range of chiral 1,4-enynes were obtained in moderate to good yields with high levels of enantioselectivity.

Deconstructive di-functionalization of unstrained, benzo cyclic amines by C-N bond cleavage using a recyclable tungsten catalyst.

With HWO as the catalyst and HO as the oxidant, we herein report a deconstructive difunctionalization of the C-N bond in unstrained, benzo cyclic amines to generate an ester group and nitro group simultaneously. The preliminary mechanistic studies suggested that the corresponding hydroxamic acid is the key intermediate for this transformation. Importantly, with the utilization of this transformation, we achieved an interesting approach for the ring contraction of quinoline to indole, an example of scaffold hopping in a hetero-aromatic system.

Intermolecular C-H Amidation of (Hetero)arenes to Produce Amides through Rhodium-Catalyzed Carbonylation of Nitrene Intermediates.

Amide bond formation is one of the most important reactions in organic chemistry because of the widespread presence of amides in pharmaceuticals and biologically active compounds. Existing methods for amides synthesis are reaching their inherent limits. Described herein is a novel rhodium-catalyzed three-component reaction to synthesize amides from organic azides, carbon monoxide, and (hetero)arenes via nitrene-intermediates and direct C-H functionalization.

Tunneling Controls the Reaction Pathway in the Deformylation of Aldehydes by a Nonheme Iron(III)-Hydroperoxo Complex: Hydrogen Atom Abstraction versus Nucleophilic Addition.

Mononuclear nonheme iron(III)-hydroperoxo intermediates play key roles in biological oxidation reactions. In the present study, we report the highly intriguing reactivity of a nonheme iron(III)-hydroperoxo complex, [(TMC)Fe(OOH)] (1), in the deformylation of aldehydes, such as 2-phenylpropionaldehyde (2-PPA) and its derivatives; that is, the reaction pathway of the aldehyde deformylation by 1 varies depending on reaction conditions, such as temperature and substrate. At temperature above 248 K, the aldehyde deformylation occurs predominantly via a nucleophilic addition (NA) pathway.

GaCl-Catalyzed C-H Cyanation of Indoles with N-Cyanosuccinimide.

An efficient GaCl-catalyzed direct cyanation of indoles and pyrroles using bench-stable electrophilic cyanating agent N-cyanosuccinimide was achieved and afforded 3-cyanoindoles and 2-cyanopyrroles in good yields and excellent regioselectivities. Notably, this protocol exhibited high reactivity for unprotected indoles and was applicable to a broad range of indole and pyrrole substrates.

Photodriven Oxidation of Water by Plastoquinone Analogs with a Nonheme Iron Catalyst.

Photoirradiation of an acetonitrile solution containing p-benzoquinone derivatives (X-Q) as plastoquinone analogs, a nonheme iron(II) complex, [(N4Py)Fe] (N4Py = N, N-bis(2-pyridylmethyl)- N-bis(2-pyridyl)methylamine), and HO afforded the evolution of O and the formation of the corresponding hydroquinone derivatives (X-QH) quantitatively. During the photodriven oxidation of water by X-Q, [(N4Py)Fe] was oxidized by the excited state of X-Q to produce the iron(IV)-oxo complex ([(N4Py)Fe(O)]) quantitatively. The concentration of [(N4Py)Fe(O)] remained virtually the same during the repeated cycles of photodriven oxidation of water by X-Q.

Catalytic Asymmetric Cascade Cyclization for Constructing Three Contiguous Stereocenters in Pyrrolobenzodiazepine-Based Cyclopentanones.

A chiral Brønsted acid catalyzed highly enantio- and diastereoselective cascade cyclization has been developed to streamline the synthesis of valuable multifunctionalized enantioenriched cyclopenta[ f]pyrrolo[1,2- d][1,4]diazepinones bearing three contiguous stereocenters in high yields with excellent control of stereochemistry from a wide range of both readily available 2-furylcarbinols and (1 H-pyrrol-1-yl)anilines, which represents the first asymmetric intramolecular conjugate addition of α,β-unsaturated cycloketones with inert N-substituted pyrroles as well as the first enantioselective aza-piancatelli rearrangement/Friedel-Crafts alkylation cascade reaction.

Facile synthesis of ordered mesoporous zinc alumina catalysts and their dehydrogenation behavior.

Ordered mesoporous Zn/AlO materials with varying Zn content were simply prepared an evaporation-induced self-assembly (EISA) method. Dehydrogenation of isobutane to isobutene was carried out on these materials; an isobutane conversion of 45.0% and isobutene yield of 39.

Reductive N-methylation of quinolines with paraformaldehyde and H for sustainable synthesis of N-methyl tetrahydroquinolines.

A new and straightforward method was developed for the synthesis of N-methyl-1,2,3,4-tetrahydroquinolines by one-pot reductive N-methylation of quinolines with paraformaldehyde and H over Pd/C catalyst. A series of functional MTHQs, including (±)-galipinine and (±)-angustrureine were successfully synthesized in good to excellent yields by applying this simple catalyst system.

Palladium-Catalyzed Enantioselective C-H Aminocarbonylation: Synthesis of Chiral Isoquinolinones.

A Pd-catalyzed enantioselective C-H carbonylation by desymmetrization was developed with commercially available L-pyroglutamic acid as chiral ligand. Isoquinolinones were successfully obtained with good yields and high enantioselectivities. Mechanistic studies and DFT calculations provided a reasonable reaction pathway.

Pd/Cu Cocatalyzed Oxidative Tandem C-H Aminocarbonylation and Dehydrogenation of Tryptamines: Synthesis of Carbolinones.

The Pd/Cu cocatalyzed oxidative tandem C-H aminocarbonylation and dehydrogenation was developed, affording carbolinones with molecular oxygen as the terminal oxidant. Natural product strychnocarpine and its derivatives were prepared conveniently using this strategy.

Brønsted acid-catalyzed aromatic annulation of alkoxyallenes with naphthols: a reaction sequence to larger π-conjugated naphthopyrans with aggregation-induced emission characters.

A practical and readily scalable reaction sequence was developed for the straightforward synthesis of a new family of larger π-conjugated naphthopyrans by a Brønsted acid-catalyzed aromatic annulation of alkoxyallenes with inert naphthols. The cascade pathway involves allylation/cyclization/debenzyloxylation/isomerization/dehydration. The new class of solid state diphenylmethylene substituted naphthopyrans are fluorescent emissive and proved to have aggregation-induced emission (AIE) behavior.

Atomically Dispersed Ruthenium Species Inside Metal-Organic Frameworks: Combining the High Activity of Atomic Sites and the Molecular Sieving Effect of MOFs.

Incorporating atomically dispersed metal species into functionalized metal-organic frameworks (MOFs) can integrate their respective merits for catalysis. A cage-controlled encapsulation and reduction strategy is used to fabricate single Ru atoms and triatomic Ru clusters anchored on ZIF-8 (Ru @ZIF-8, Ru @ZIF-8). The highly efficient and selective catalysis for semi-hydrogenation of alkyne is observed.

Nickel-Catalyzed Kumada Coupling of Boc-Activated Aromatic Amines via Nondirected Selective Aryl C-N Bond Cleavage.

A nickel-catalyzed Kumada coupling of aniline derivatives was developed by selective cleavage of aryl C-N bonds under mild reaction conditions. Without preinstallation of an ortho directing group on anilines, the cross-coupling reactions of Boc-protected aromatic amines with aryl Grignard reagents afforded unsymmetric biaryls. Mechanistic studies by DFT calculations revealed that the nickel-mediated C-N bond cleavage is the rate-limiting step.

Heme and Nonheme High-Valent Iron and Manganese Oxo Cores in Biological and Abiological Oxidation Reactions.

Utilization of O as an abundant and environmentally benign oxidant is of great interest in the design of bioinspired synthetic catalytic oxidation systems. Metalloenzymes activate O by employing earth-abundant metals and exhibit diverse reactivities in oxidation reactions, including epoxidation of olefins, functionalization of alkane C-H bonds, arene hydroxylation, and -dihydroxylation of arenes. Metal-oxo species are proposed as reactive intermediates in these reactions.

Unified Mechanism of Oxygen Atom Transfer and Hydrogen Atom Transfer Reactions with a Triflic Acid-Bound Nonheme Manganese(IV)-Oxo Complex via Outer-Sphere Electron Transfer.

Outer-sphere electron transfer from styrene, thioanisole, and toluene derivatives to a triflic acid (HOTf)-bound nonheme Mn(IV)-oxo complex, [(N4Py)Mn(O)]-(HOTf) (N4Py = N, N-bis(2-pyridylmethyl)- N-bis(2-pyridyl)methylamine), has been shown to be the rate-determining step of different types of redox reactions such as epoxidation, sulfoxidation, and hydroxylation of styrene, thioanisole, and toluene derivatives, respectively, by [(N4Py)Mn(O)]-(HOTf). The rate constants of HOTf-promoted epoxidation of all styrene derivatives with [(N4Py)Mn(O)] and electron transfer from electron donors to [(N4Py)Mn(O)] exhibit a remarkably unified correlation with the driving force of outer-sphere electron transfer in light of the Marcus theory of electron transfer. The same electron-transfer driving force dependence is observed in the oxygen atom transfer from [(N4Py)Mn(O)]-(HOTf) to thioanisole derivatives as well as in the hydrogen atom transfer from toluene derivatives to [(N4Py)Mn(O)]-(HOTf).

Manganese-Catalyzed Asymmetric Oxidation of Methylene C-H of Spirocyclic Oxindoles and Dihydroquinolinones with Hydrogen Peroxide.

A highly efficient strategy for the enantioselective oxidation of methylene C-H of spirocyclic oxindoles and dihydroquinolinones has been established, in which an earth-abundant manganese catalyst and hydrogen peroxide are used. Noteworthy, the manganese catalyst can be applied to the asymmetric hydroxylation of spirocyclic 2,3-dihydroquinolin-4-ones with 94-99% ee.