The Electrochemical Characterization of Single Core–Shell Nanoparticles

We report the direct solution‐phase characterization of individual gold‐core silver‐shell nanoparticles through an electrochemical means, with selectivity achieved between the core and shell components based on their different redox activities. The electrochemically determined core–shell sizes are in excellent agreement with electron microscopy‐based results, successfully demonstrating the electrochemical characterization of individual core–shell nanoparticles.     

Conjugate Addition versus Cycloaddition/Condensation of Nitro Compounds in Water: Selectivity,Acid–Base Catalysis,and Induction Period

Nitroacetates and nitroacetamides react in water as in chloroform with electron‐deficient dipolarophiles to give condensation or conjugate addition products under base catalysis. In general, high selectivity towards condensation is observed in water, with shorter induction periods than in chloroform. In water, condensations slowly occur even without base; kinetic profiles evidence the catalytic effect of the base, which should be related to the conversion into the tautomer nitronic acid. Condensations in water provide convenient access to isoxazole derivatives bearing various functional groups including ammonium, carboxy, and carboxyamide.     

A General Approach to the Synthesis of Gold–Metal Sulfide Core–Shell and Heterostructures

Cores and effect : Water‐dispersible core–shell structures and heterostructures incorporating gold nanocrystals of different shapes (polyhedra, cubes, and rods) and a variety of transition metal sulfide semiconductors (ZnS, CdS, NiS, Ag₂S, and CuS) are synthesized using cetyltrimethylammonium bromide‐encapsulated gold nanocrystals and metal thiobenzoates as starting materials.

     

Bioinspired Core–Shell Nanoparticles for Hydrophobic Drug Delivery

A large range of nanoparticles have been developed to encapsulate hydrophobic drugs. However, drug loading is usually less than 10 % or even 1 %. Now, core–shell nanoparticles are fabricated having exceptionally high drug loading up to 65 % (drug weight/the total weight of drug‐loaded nanoparticles) and high encapsulation efficiencies (>99 %) based on modular biomolecule templating. Bifunctional amphiphilic peptides are designed to not only stabilize hydrophobic drug nanoparticles but also induce biosilicification at the nanodrug particle surface thus forming drug‐core silica–shell nanocomposites. This platform technology is highly versatile for encapsulating various hydrophobic cargos. Furthermore, the high drug loading nanoparticles lead to better in vitro cytotoxic effects and in vivo suppression of tumor growth, highlighting the significance of using high drug‐loading nanoparticles.     

Synthesis of the Hemoglobin‐Conjugated Polymer Micelles by Thiol Michael Addition Reactions

Amphiphilic triblock copolymers mPEG‐b‐PMAC‐b‐PCL are synthesized using methoxyl poly(ethylene glycol), cyclic carbonic ester monomer including acryloyl group, and ε‐caprolactone. Copolymers are self‐assembled into core–shell micelles in aqueous solution. Thiolated hemoglobin (Hb) is conjugated with micelles sufficiently through thiol Michael addition reaction to form hemoglobin nanoparticles (HbNs) with 200 nm in diameter. The conjugation of Hb onto the micelle surface is further confirmed by X‐ray photoelectron spectroscopy. Feeding ratio of copolymer micelles to Hb at 1:3 would lead to the highest hemoglobin loading efficiency 36.7 wt%. The UV results demonstrate that the gas transporting capacity of HbNs is well remained after Hb is conjugated with polymeric micelles. Furthermore, the obtained HbNs have no obvious detrimental effects on blood components in vitro. This system may thus have great potential as one of the candidates to be developed as oxygen carriers and provide a reference for the modification of protein drugs.

     

Direct Catalytic Asymmetric Vinylogous Conjugate Addition of Unsaturated Butyrolactones to α,β‐Unsaturated Thioamides

Soft Lewis acid/Brønsted base cooperative catalysts have enabled direct catalytic asymmetric vinylogous conjugate addition of α,β‐ and β,γ‐unsaturated butyrolactones to α,β‐unsaturated thioamides with perfect atom economy. When using α‐angelica lactone and its derivatives as pronucleophiles, as little as 0.5 mol % catalyst loading was sufficient to complete the reaction necessary to construct consecutive tri‐ and tetrasubstituted stereogenic centers in a highly diastereo‐ and enantioselective fashion.     

Synthesis and Characterization of Dendrimer‐Encapsulated Bimetallic Core‐Shell PdPt Nanoparticles

Using a successive method, PAMAM dendrimer‐encapsulated bimetallic PdPt nanoparticles have been successfully prepared with core‐shell structures (Pd@Pt DENs). Evidenced by UV‐vis spectra, high resolution transmission electron microscopy, and X‐ray energy dispersive spectroscopy (EDS), the obtained Pd@Pt DENs are monodispersed and located inside the cavity of dendrimers, and they show a different structure from monometallic Pt or Pd and alloy PdPt DENs. The core‐shell structure of Pd@Pt DENs is further confirmed by infrared measurements with carbon monoxide (IR‐CO) probe. In order to prepare Pd@Pt DENs, a required Pd/Pt ratio of 1:2 is determined for the Pt shell to cover the Pd core completely. Finally, a mechanism for the formation of Pd@Pt DENs is proposed.     

Cerium Alkoxides—Synthesis, Properties and Their Use in Michael Addition Reaction

Cerium(III) alkoxides served as an effective and attractive promoter for the Michael addition reaction with excellent chemical yields under mild conditions in short reaction time.     

Formation of Quaternary Stereogenic Centers by Copper‐Catalyzed Asymmetric Conjugate Addition Reactions of Alkenylaluminums to Trisubstituted Enones

Alkenylaluminums undergo asymmetric copper‐catalyzed conjugate addition (ACA) to β‐substituted enones allowing the formation of stereogenic all‐carbon quaternary centers. Phosphinamine–copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β‐substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl‐ and alkyl‐substituted alkenyl nucleophiles. Moreover, alkyl‐substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu‐catalyzed ACA.     

Mechanochemistry and Eco-Bases for Sustainable Michael Addition Reactions

The Michael addition reaction was revisited with a full focus on sustainability combined with efficiency, using mechanochemistry in mild conditions. First, the synthesis of cyclopentenone derivatives was chosen as a model reaction to find optimal conditions in mechanochemistry while using classical but weak bases. The reaction was efficient (84–95% yields), fast (2–6 h), solvent free, and required 0.1 equivalent of base. Aiming to reach greener conditions, classical bases were then replaced using new bio-sourced bases, called Eco-bases, that were easily prepared from plants and led to heterogeneous catalysts. The composition and structure of Eco-bases were characterized by MP-AES, XRPD, EBSD/EDS, HRTEM/EDX and ion chromatography. Interestingly, a high ratio of potassium was observed with the presence of K₂Ca(CO₃)₂ for the most effective Eco-base. The new Eco-bases were used for the mechanical-assisted construction of functionalized alkenone derivatives. The versatility of the method has been successfully applied with good to excellent yields to different Michael donors and acceptors. Eco-bases were recycled and reused four times with the same performances. Combining Eco-bases and mechanochemistry in Michael addition reactions allowed reaching a maximum degree of sustainability (efficient, rapid, low catalyst loading, solvent-free reactions with bio-sourced catalysts) and participating in the development of mechanochemistry in sustainable chemistry.