Eu Ions Site-selective Doping and Nonstoichiometric Chemistry of NaTaO3 in Na-rich Environment

The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3＋ ions selectively located in Ta and Na sites, respectively, the band gaps of two Eu-doped NaTaO3 models were all narrowed, which were assigned to lattice defects and impurity band of the Eu dopent. For the model of Eu3＋ ions located in the Na＋ sites of NaTaO3, the new impurity band mainly composited of Eu 4f orbital appeared at the top over the valence band, indicating the enhanced oxidative ability. For the model of Eu3＋ ions located in the Ta5＋ sites of NaTaO3, a midgap state generated was located at the bottom of conduct band and the band potential shifted up, confirming the strong reductive ability in the Na-rich enviornment. The densities of electron states were significantly increased in both the conduction and valence bands in Na-rich model, which resulted in the increased carrier migration rate and thus photocatalytic activity enhancement. It is proposed that Eu3＋ ions doping at the Ta sites could enhance the reduced photocatalytic performance via controlling the nonstoichiometric Na/Ta molar ratio in the Eu-doped NaTaO3 system.

Engineering surface strain for site-selective island growth of Au on anisotropic Au nanostructures

Controlled growth of islands on plasmonic metal nanoparticles represents a novel strategy in creating unique morphologies that are difficult to achieve by conventional colloidal synthesis processes,where the nanoparticle morphologies are typically determined by the preferential development of certain crystal facets.This work exploits an effective surface-engineering strategy for site-selective island growth of Au on anisotropic Au nanostructures.Selective ligand modification is first employed to direct the site-selective deposition of a thin transition layer of a secondary metal,e.g.,Pd,which has a considerable lattice mismatch with Au.The selective deposition of Pd on the original seeds produces a high contrast in the surface strain that guides the subsequent site-selective growth of Au islands.This strategy proves effective in not only inducing the island growth of Au on Au nanostructures but also manipulating the location of grown islands.By taking advantage of the iodide-assisted oxidative ripening process and the surface strain profile on Au nanostructures,we further demonstrate the precise control of the islands’number,coverage,and wetting degree,allowing fine-tuning of nanoparticles’optical properties.

Site-Selective Palladium-Catalyzed 1,1-Arylamination of Terminal Alkenes

Many of the commonly used pharmaceuticals and biologically active natural products are nitrogencontaining compounds.Recently,the transitionmetal-catalyzed or the radical-mediated 1,2-carboamination of alkenes has been well explored to access amine scaffolds.However,synthetic strategies toward the 1,1-carboamination of alkenes are severely limited.Herein,we describe a method to achieve the 1,1-arylamination using readily available building blocks enabled by palladium catalysis.This sequential three step-Heck arylation,metal migration,followed by aza-1,6-Micheal addition process exhibits excellent chemo-and regioselectivity.To showcase the potential as a method for diversity-oriented drug discovery,the modification of numerous structurally complex bioactive molecules was also successfully performed.

Weakly coordinating group directed rhodium-catalyzed unconventional site-selective C-H olefination of indolizines at the 8-position

A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additive under similar reaction conditions.Weakly coordinating groups,such as ketone,alde hyde,amide and ester,were used as directing groups.The ester group can be removed under acid conditions and therefore is used as a traceless directing group.

Site selective 5f electronic correlations inβ-uranium

We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.

Highly Oriented ZnO Rod Arrays on Si Substrates from Aqueous Solution

Ordered zinc oxide （ZnO） rod arrays with very high orientation were fabricated on Si substrates by using a solution method. The substrate surfaces were functionalized by Self-Assembly Monolayers （SAMs）. In the very early growth stage, the oriented ZnO crystals had already grown, which appeared to be the main reason why ZnO nanorods showed very high orientation. The un-dense and un-uniform SAMs provided a surface that was heterogeneous to ZnO nucleation. Consequently, highly oriented ZnO rods were selectively grown on the ＂coin-like＂ SAM-uncovered regions. The route developed here can provide some helpful information to control the nucleation and orientation of ZnO in aqueous solution. Also, the site-selective growth mechanisms can indicate a clue to grow patterned highly oriented ZnO nanorod arrays by the organic template.

Sol-Gel Preparation and Phase Transition of RE Orthoborates

The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different dependence on the preparing conditions, The photoluminescent spectra indicate that there are more than two sites for Eu3+ in the sol-gel prepared polycrystalline YBO3:Eu with low-symmetry.

Transition-metal-catalyzed remote meta-C-H alkylation and alkynylation of aryl sulfonic acids enabled by an indolyl template

Transition-metal-catalyzed remote sp^(2)C-H functionalization of aryl sulfonic acids was hardly ever real-ized owing to competitive ortho-C-H functionalization of aryl sulfonates and electron-deficient nature of phenyl ring.Herein,with the assistance of a practical biaryl indolyl directing template,palladium-catalyzed remote sp^(2)C-H alkylation of aryl sulfonic acids have been achieved in moderate to good yields with exclusive meta selectivity.Moreover,remote meta-selective C-H alkynylation of aryl sulfonic acids was also accomplished with a rhodium catalyst.These meta-C-H functionalized products proved to be the superior synthetic precursors,which are difficult to access using the conventional strategy.

Chiral AuCu heterostructures with site-specific geometric control and tailored plasmonic chirality

Rational design and construction of chiral-achiral hybrid structures are of great importance to realize the multifunctional complex chiral structures toward emerging technological applications. However, significant challenges remain due to the lack of fine control over the heterostructure. Here, we have developed a general bottom-up synthetic strategy for the site-selective growth of Cu nanodomains on intrinsically chiral Au nanocrystals. Chiral AuCu heterostructures with three distinct architectures were achieved by controlling the overgrowth of Cu nanodomains in a site-specific manner. The geometry-dependent plasmonic chirality of the heterostructures was demonstrated experimentally by circular dichroism spectroscopy and theoretically through finite-difference time-domain simulations. The site-specific geometric control of chiral AuCu heterostructures was also extended to employ anisotropic chiral Au nanoplates and nanorods as the building blocks. By virtue of the galvanic replacement reactions between metal ions and Cu atoms, chiral heterostructures with increasing architectural complexity and compositional diversity can be further achieved. The current work not only opens up a promising strategy to synthesize complex chiral hybrid nanostructures but also provides an important knowledge framework that guides the rational design of multifunctional chiral hybrid nanostructures toward chiroptical applications.

Highly selective synthesis of functionalized morphan derivatives through a multi-component cascade reaction of 3-formylchromones, 2-naphthols, and enaminones

A novel protocol for the preparation of highly functionalized 2-azabicyclo[3.3.1]nonane(morphan)derivatives via a multicomponent cascade reaction,involving 3-formylchromones,2-naphthols,and enaminones in the ionic liquid[BMIM]PF6 as the solvent and promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU),was developed,which involved the cleavage of one C–O bond and formation of four bonds(1 C–O,1 C–N,and 2 C–C bonds).As a result,a series of morphan derivatives were produced through a cascade reaction,including a sequence of 1,2-addition,enol-keto tautomerization,Michael addition,dehydration,another Michael addition,imine-enamine tautomerization,and N-alkylation reactions,which were accompanied by a ring-opening reaction.This protocol was suitable for combinatorial and parallel syntheses of natural product-like morphan compounds in a one-pot reaction rather than through tedious multi-step reactions.

Protection-Free Site-Directed Peptide or Protein S-Glycosylation and Its Application in the Glycosylation of Glucagon-like Peptide 1

The development of a facile cysteine-directed S-glycosylation strategy would facilitate the intensive investigation of the effect of glycosylation on protein translational modification.Herein,we introduce glycosyl Bunte salt as an efficient glycosyl donor for site-selective peptide/protein modification.The coupling reaction with cysteine thiols under alkaline buffer conditions proceeded chemoselectively,delivering homogeneous glycoconjugates and inorganic salt as the only byproduct.A series of sugar moieties,including monosaccharides and oligosaccharides,were successfully conjugated to the peptides and protein via the disulfide bond.Furthermore,this protocol was applied to the glycosylation of the glucagon-like peptide 1(GLP-1)variant,and its glycosylated effect on blood glucose control was also studied.

A mini-review on the enzyme-mediated manipulation of proteins/peptides

Recent years have seen an ever increasing number of enzyme mediated protein/peptide modification reactions, which contribute significantly to the elucidation of related biological functions. The many available enzymes have, however, caused difficulties for practitioners in choosing the most appropriate enzyme for a certain purpose. This review surveyed the widely used enzymes(i.e., sortases, butelase 1,subtiligase, formylglycine generating enzyme and farnesyltransferase) in the manipulation of proteins/peptides, and the application fields of these enzymes as well as the advantages and limitations of each enzyme are summarized.

Arene C-H Iodination Using Aryl Iodides

Metathesis reactions represent powerful synthetic tools that have been used in a number of fields from the synthesis of natural product to functional material preparation.However,the C-H metathesis reaction is extremely rare.Herein,we report the first Pd(Ⅱ)-catalyzed C-H iodination of arenes using 2-nitrophenyl iodides as the mild iodinating reagents via a formal metathesis reaction.Unusual C-I bond formation occurred with aryl iodides in preference to competing C-C coupling in this reaction.Assisted by aliphatic carboxyl directing groups,a range of hydrocinnamic acids and related arenes could be selectively iodinated at either meta-or orthopositions of the phenyl ring.Remote diastereoselective C-H activation was also promising.This method might unfold a novel approach to iodinate challenging substrates.

Recent Advances in Asymmetric Transformations of Unactivated Alkanes and Cycloalkanes through Direct C—H Functionalization

The direct conversion of unactivated alkanes and cycloalkanes into structurally diverse molecules through aliphatic C—H functionalization is a useful process, which has attracted intense interest from academia and industry. Methods to control chemo- and site-selectivity, combined with asymmetric catalysis, provide appealing access to high value-added enantiomer-enriched compounds but are far less developed. This review focuses on recent progress in (i) asymmetric reactions of alkanes or cycloalkanes with prochiral substrates which generate a stereocenter adjacent to the cleaved C(sp3)–H bond, and (ii) C(sp3)–H enantiodiscriminatory reactions creating a new stereogenic center on the carbon of a cleaved C(sp3)–H bond. Elegant strategies are discussed, including (a) metal carbene-induced C—H insertions by chiral rhodium catalysts, (b) metal-oxo-mediated C—H oxidation by biomimetic manganese catalysts, (c) enzyme catalysis by cytochromes P450 variants, and (d) dual catalysis by a photocatalyst and a chiral Lewis acid (CLA) or a chiral phosphoric acid (CPA). These catalytic systems can not only precisely recognize primary, secondary and tertiary C—H bonds at specific positions in alkanes and cycloalkanes, but also support a high level of stereoselectivity in the reactions. It is expected that the advances will stimulate further progress in asymmetric catalysis, synthetic methodology, pharmaceutical development and industrial processes.

Walking Cations: Transition-Metal Free Benzyl Cation-Triggered sp^(2) C—H Phosphorylation and Etherification

A novel benzyl cation-triggered site-selective sp^(2) C—H phosphorylation and etherification was developed. This reaction was conducted under the transition metal-free conditions through cation migration via dearomatization. Under the reaction conditions, the derivatives of naphthalenes, benzofurans and benzo[b]thiophenes all can be transformed into the corresponding products in good to excellent yields. It provides a method to construct sp^(2) C—P and sp^(2) C—O bonds as well as a new strategy for benzylic activation-triggered sp^(2) C—H functionalization.