d-Orbital Reconstructions Forced by Double Bow-Shaped Deformations and Second Coordination Sphere Effects of Cu(II) Heme Analogs in HER.

Both geometric architecture and electronic configurations of heme proteins contribute to its activity. In this work we designed and synthesized a series of four copper(II) porphyrin complexes (4-, 3-, 2- and 1-Cu) where the molecular conformations are modulated by a pair of stepwise shortened straps on the same porphyrin side (cis-ortho) to give double bow-shaped skeletons. Single crystal structures demonstrate that the straps gradually increase the saddle deformation and the deviation of the metal centers, which is in accordance with two, unusual d-orbital reconstructions of two different ground states, as revealed by 4 K EPR and DFT calculations.

A cooperative Pd/Co catalysis system for the asymmetric (4+2) cycloaddition of vinyl benzoxazinones with -acylpyrazoles.

Transition metal-catalyzed cycloaddition has been established as a powerful tool for heterocycle synthesis. Despite impressive advances, the exploitation of new catalysis strategies and systems is still highly significant to enrich the heterocycle family. Herein, we disclosed a cooperative catalysis system merging an achiral Pd catalyst and a chiral Co catalyst for the asymmetric [4+2] cycloaddition between vinyl benzoxazinones and -acylpyrazoles.

Sustainable Route Toward N-Boc Amines: AuCl /CuI-Catalyzed N-tert-butyloxycarbonylation of Amines at Room Temperature.

N-tert-butoxycarbonyl (N-Boc) amines are useful intermediates in synthetic/medicinal chemistry. Traditionally, they are prepared via an indirect phosgene route with poor atom economy. Herein, a step- and atom-economic synthesis of N-Boc amines from amines, t-butanol, and CO was reported at room temperature.

Manganese-Catalyzed [4 + 2] Annulation of N-H Amidines with Vinylene Carbonate via C-H Activation.

Manganese-catalyzed C-H bond functionalization of aryl amidines for the synthesis of 1-aminoisoquinolines in the presence of vinylene carbonate has been developed. The reaction features a broad substrate scope and proceeds under mild reaction conditions with only the carbonate anion as the byproduct.

Iridium-Catalyzed Asymmetric Transfer Hydrogenation of Quinolines in Biphasic Systems or Water.

An asymmetric transfer hydrogenation (ATH) of quinolines in water or biphasic systems was developed. This ATH reaction proceeds smoothly without the need for inert atmosphere protection in the presence of a water-soluble iridium catalyst, which bears an easily available aminobenzimidazole ligand. This ATH system can work at a catalyst loading of 0.

Brønsted-acid sites promoted degradation of phthalate esters over MnO: Mineralization enhancement and aquatic toxicity assessment.

Advanced oxidation processes (AOPs) are important technologies for aqueous organics removal. Despite organic pollutants can be degraded via AOPs generally, high mineralization of them is hard to achieve. Herein, we synthesized a manganese oxide nanomaterial (H2-OMS-2) with abundant Brønsted-acid sites via ion-exchange of cryptomelane-type MnO (OMS-2), and tested its catalytic performance for the degradation of phthalate esters via peroxymonosulfate (PMS) activation.

Enantioselective Construction of Axially Chiral Azepine-Containing P,N-Ligands from l-Alanine.

A family of axially chiral azepine-containing seven-membered cyclic P,N-ligands (named Indole-azepinap) have been prepared by using l-alanine as an original chirality source. The direct chromatographic separation of two diastereomeric phosphine oxides on silica gel enabled these ligands to be easy available, allowing further structural and electronic modifications. Preliminary application of these Indole-azepinaps has been demonstrated in a Pd-catalyzed asymmetric allylic alkylation with high yields and moderate enantioselectivities.

Site-Fixed Hydroboration of Terminal and Internal Alkenes using BX / Pr NEt*.

An unprecedented and general hydroboration of alkenes with BX (X=Br, Cl) as the boration reagent in the presence of Pr NEt is reported. The addition of Pr NEt not only suppresses alkene polymerization and haloboration side reactions but also provides an "H" source for hydroboration. More importantly, the site-fixed installation of a boryl group at the original position of the internal double bond is readily achieved in contrast to conventional transition-metal-catalyzed hydroboration processes.

Simultaneous Tuning Band Gaps of Cu O and TiO to Form S-Scheme Hetero-Photocatalyst.

Photocatalytic Z or S scheme merits higher redox potentials and faster charge separation. However, heterostructure photocatalysts with band gaps of bulk materials often have a type I band structure leading to poor photocatalytic activity. In view of this, we report simultaneous tuning of band gaps of Cu O and TiO , where quantum dot Cu O nanoparticles were formed on doped TiO with Ti .

Electrochemical Approaches to Carbonylative Coupling Reactions.

The carbonylation reaction is an effective way to introduce CO or other carbonyl groups into organic compounds, and widely used in the preparation of aldehydes, ketones, amides, and esters. The replacement of conventional reaction approaches by greener electrochemical methods is appealing with great synthetic potential as well as inherent safety, owing to the avoidance of external oxidants or reductants and a more facile control in product selectivity. In this minireview, we give a summary of the recent development of carbonylation reactions via the electrochemical approach.

Hierarchical Zeolites-confined Metal Catalysts and Their Enhanced Catalytic Performances.

The confinement of metal species within hierarchical zeolites combines the acidic/basic sites of zeolites, the enhanced mass transfer of mesoporous system, and the inside active metal sites, leading to high activity, unique selectivity, and superior stability in chemicals synthesis, energy and environment catalysis. To date, review on this emerging topic is rarely reported. Herein, we classify five metals-hierarchical zeolites composite (metal@hierarchical zeolites) according to the location of metals on hierarchical structure, including metals located on micropores, intercrystalline mesopores, intracrystalline mesopores, hollow nanobox and mesoporous shells.

Size-Dependent Selectivity of Electrochemical CO Reduction on Converted In O Nanocrystals.

The size modulation of catalyst particles represents a useful dimension to tune catalytic performances by impacting not only their surface areas but also local electronic structures. It, however, has remained inadequately explored and poorly elucidated. Here, we report the interesting size-dependent selectivity of electrochemical CO reduction on In O nanocrystals.

Highly Regio- and Enantioselective Reductive Coupling of Alkynes and Aldehydes via Photoredox Cobalt Dual Catalysis.

A Co-catalyzed highly regio- and enantioselective reductive coupling of alkynes and aldehydes has been developed under visible light photoredox dual catalysis. A variety of enantioenriched allylic alcohols have been obtained by using unsymmetrical internal alkynes and commercially available catalyst, chiral ligand, and reagents. It is noteworthy that this approach has considerable advantages, such as excellent regio- (>95:5 for >40 examples), stereo- (up to >95:5 /), and enantioselectivity (92-99% ee, >35 examples) control, mild reaction conditions, broad substrate scope, and good functional group compatibility, making it a great improvement to enantioselective alkyne-aldehyde reductive coupling reactions.

Defective acidic 2D COF-based catalysts for boosting the performance of polyoxymethylene diethyl ether synthesis under mild conditions.

Polyoxymethylene diethyl ethers (PODEEn) are oxygenated fuel additives with high performance due to their advantageous fuel properties. PODEEn can alleviate carbon debt as the production can utilize bioethanol and biomass syngas. Heterogeneous solid acid catalysts are desirable for an efficient PODEEn synthesis.

Enhancing stability by trapping palladium inside N-heterocyclic carbene-functionalized hypercrosslinked polymers for heterogeneous C-C bond formations.

Catalyst deactivation caused by the aggregation of active metal species in the reaction process poses great challenges for practical applications of supported metal catalysts in solid-liquid catalysis. Herein, we develop a hypercrosslinked polymer integrated with N-heterocyclic carbene (NHC) as bifunctional support to stabilize palladium in heterogeneous C-C bond formations. This polymer supported palladium catalyst exhibits excellent stability in the one-pot fluorocarbonylation of indoles to four kinds of valuable indole-derived carbonyl compounds in cascade or sequential manner, as well as the representative Suzuki-Miyaura coupling reaction.

Enantioselective Radical Carbocyanation of 1,3-Dienes via Photocatalytic Generation of Allylcopper Complexes.

1,3-Dienes are readily available feedstocks that are widely used in the laboratory and industry. However, the potential of converting 1,3-dienes into value-added products, especially chiral products, has not yet been fully exploited. By synergetic photoredox/copper catalysis, we achieve the first visible-light-induced, enantioselective carbocyanation of 1,3-dienes by using carboxylic acid derivatives and trimethylsilyl cyanide.

Selectivity-tunable oxidation of tetrahydro-β-carboline over an OMS-2 composite catalyst: preparation and catalytic performance.

Controlling the reaction selectivity of organic transformations without losing high conversion is always a challenge in catalytic processes. In this work, a H3PO4·12WO3/OMS-2 nanocomposite catalyst ([PW]-OMS-2) was prepared through the oxidation of a Mn(ii) salt with sodium phosphotungstate by KMnO4. Comprehensive characterization indicates that different Mn2+ precursors significantly affected the crystalline phase and morphology of the as-synthesized catalysts and only MnSO4·H2O as the precursor could lead to a cryptomelane phase.

Catalytic Boration of Alkyl Halides with Borane without Hydrodehalogenation Enabled by Titanium Catalyst.

An unprecedented and general titanium-catalyzed boration of alkyl (pseudo)halides (alkyl-X, X=I, Br, Cl, OMs) with borane (HBpin, HBcat) is reported. The use of titanium catalyst can successfully suppress the undesired hydrodehalogenation products that prevail using other transition-metal catalysts. A series of synthetically useful alkyl boronate esters are readily obtained from various (primary, secondary, and tertiary) alkyl electrophiles, including unactivated alkyl chlorides, with tolerance of other reducing functional groups such as ester, alkene, and carbamate.

High Chemo-/Stereoselectivity for Synthesis of Polysubstituted Monofluorinated Pyrimidyl Enol Ether Derivatives.

A novel intramolecular Smiles rearrangement of α-fluoro-β-keto-pyrimidylsulfones (usually used as a carbon nucleophile) was developed, providing a versatile avenue for synthesis of tri/tetra-substituted monofluorinated pyrimidyl enol ethers. Among these, diverse ()-monofluorovinylsulfones and sulfinates were efficiently assembled by adding extra electrophile and fine-tuning reaction conditions. The process is triggered by a keto-enol tautomerism from enol oxyanion to pyrimidine 2-carbon, completely different from the classical carbon nucleophilic addition reaction approach.

Enantioselective Construction of C-C Axially Chiral Quinazolinones via Chirality Exchange and Phase-Transfer Catalysis.

A family of axially chiral quinazolinone-based heterobiaryls were constructed with high levels of enantiocontrol (up to 94% ee). Convergently, three different synthetic methods have been realized to prepare these valuable compounds including central-to-axial chirality transfer, dynamic kinetic resolution, and phase-transfer catalysis. Importantly, novel P,N-ligands with a π-π stacking can be derived from heterobiaryls by chirality exchange strategy or synthesized directly from complementary phase-transfer catalysis by using the inexpensive chiral quaternary ammonium salt.

Enantioselective Construction of Quinoxaline-Based Heterobiaryls and P,N-Ligands via Chirality Transfer Strategy.

Central-to-axial chirality transfer via C-N single bond oxidation was first achieved as a versatile and conceptually distinct strategy to prepare a new family of axially chiral heteroaromatic biaryl backbones and P,N-ligands (named as Quinoxalinaps) in gram scale. Two atropisomers of Quinoxalinaps (ee >99%) were readily accessed from the same precursor enantiomer by a simple dehydrogenative oxidation with MnO and -BuOOH under mild conditions. Phosphine could be introduced into the ligands before or after the chirality control process.

A DFT study on the C-H oxidation reactivity of Fe(iv)-oxo species with N4/N5 ligands derived from l-proline.

The hydroxylation of hexane by two FeO complexes bearing a pentadentate ligand (N5, Pro3Py) and a tetradentate ligand (N4, Pro2PyBn) derived from l-proline was studied by DFT calculations. Theoretical results predict that both FeO complexes hold triplet ground states. The hydrogen atom abstraction (HAA) processes by both FeO species proceed through a two-state reactivity, thus indicating that HAA occurs a low-barrier quintet surface.

Catalytic Enantioselective Methylene C(sp)-H Hydroxylation Using a Chiral Manganese Complex/Carboxylic Acid System.

Achieving direct C-H hydroxylation in a highly diastereo- and enantioselective manner is still a challenging goal. This reaction is mainly hindered by the potential for overoxidation of the generated alcohols as well as low stereoselectivity. Herein, we present an enantioselective benzylic C-H hydroxylation catalyzed by a manganese complex, HO, and a carboxylic acid in 2,2,2-trifluoroethanol.