One‐Pot Fabrication of Rattle‐Like Capsules with Multicores by Pickering‐Based Polymerization with Nanoparticle Nucleation

Rattle‐like polymer capsules with multicores in one shell are facilely fabricated by oil‐in‐water Pickering emulsion polymerization for the first time. The oil phase contains hydrophobic silica nanoparticles dispersed in polymerizable monomer, styrene, and unpolymerizable solvent, hexadecane. The multicore rattle‐like capsules are facilely produced after the polymerization of monomers in the oil droplets. The key point of this one‐pot method lies in the nucleation of hydrophobic silica and the phase separation between the resulting polystyrene and hexadecane. The influences of the contents of silica, hexadecane, cross‐linker, and stabilizer on the structure and morphology of rattle‐like capsules are systematically investigated. Moreover, functionalization of the rattle‐like capsules can be developed easily by varying hydrophobic nucleation nanoparticles in the oil phase. This work opens up a new route to fabricate multilevel capsules or spheres.

     

Metal‐Free One‐Pot Synthesis of Benzofurans

Ethyl acetohydroxamate was efficiently arylated with diaryliodonium salts at room temperature under transition‐metal‐free conditions. The obtained O‐arylated products were reacted in situ with ketones under acidic conditions to yield substituted benzo[b]furans through oxime formation, [3,3]‐rearrangement, and cyclization in a fast and operationally simple one‐pot fashion without using excess reagents. Alternatively, the O‐arylated products could be isolated or transformed in situ to aryloxyamines or O‐arylaldoximes. The methodology was applied to the synthesis of Stemofuran A and the formal syntheses of Coumestan, Eupomatenoid 6, and (+)‐machaeriol B.     

One‐Pot Synthesis of 1,3,5‐Triarylpyrazoles

A series of novel 1,3,5‐triarylpyrazoles 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l , 3m , 3n , 3o , 3p , 3q , 3r , 3s , 3t , 3u , 3v , 3w , 3x were synthesized from flavanones, arylhydrazines, and trimethyl phosphate in an one‐pot procedure. Facile reaction process, easy after‐reaction workshop, and good yields are the distinct characteristics of the developed protocol. The target compounds were characterized by element analysis, infrared ray (IR), ¹H NMR spectra, and electrospray ionization‐mass spectrometry. The structure of representative compound 3h (C₂₃H₂₀N₂O₃, M_r = 372.42) was further confirmed by X‐ray diffraction. It crystallizes in monoclinic, space group P 2₁/c, a = 8.9720(5), b = 24.5523(13), c = 8.9687(6) Å, α = 90.0000, β = 102.6417(17), γ = 90.0000°, V = 1927.76(20) ų, Z = 4, μ(MoKα) = 0.086, F(000) = 784, D_c = 1.283 g/cm³, the final R = 0.0349 and wR = 0.0844 for 1668 observed reflections (I > 2σ(I))     

One‐Pot Sequence‐Controlled Synthesis of Oligosiloxanes

Silicones (organopolysiloxanes) have found applications in a wide range of research areas, and their unique and valuable properties have rendered these materials virtually irreplaceable. Despite the fact that silicones have been employed industrially for more than 70 years, synthetic routes to generate silicones remain limited, and the sequence‐controlled synthesis of oligo‐ and polysiloxanes still represents a major challenge in silicone chemistry. Described here is a highly selective sequence‐controlled synthesis of linear, branched, and cyclic oligosiloxanes by simple iteration of two reactions, specifically, a B(C₆F₅)₃‐catalyzed dehydrocarbonative cross‐coupling of alkoxysilanes with hydrosilanes and a B(C₆F₅)₃‐catalyzed hydrosilylation of carbonyl compounds, in a single flask. The sequence of the resulting oligosiloxanes can be controlled precisely by the order of addition of the hydrosilane monomers.     

One‐Step Microfluidic Fabrication of Polyelectrolyte Microcapsules in Aqueous Conditions for Protein Release

We report a microfluidic approach for one‐step fabrication of polyelectrolyte microcapsules in aqueous conditions. Using two immiscible aqueous polymer solutions, we generate transient water‐in‐water‐in‐water double emulsion droplets and use them as templates to fabricate polyelectrolyte microcapsules. The capsule shell is formed by the complexation of oppositely charged polyelectrolytes at the immiscible interface. We find that attractive electrostatic interactions can significantly prolong the release of charged molecules. Moreover, we demonstrate the application of these microcapsules in encapsulation and release of proteins without impairing their biological activities. Our platform should benefit a wide range of applications that require encapsulation and sustained release of molecules in aqueous environments.     

Multi‐Sensitive Microgels Filled with Conducting Poly(3,4‐ethylenedioxythiophene) Nanorods

In this work we describe the synthesis of multi‐sensitive aqueous microgel particles with incorporated conducting poly(3,4‐ethylenedioxythiophene) (PEDOT) nanorods. We demonstrate that the loaded amount of PEDOT nanorods as well as their morphology can be varied by controlling the reaction conditions such as monomer concentration and alcohol concentration in aqueous phase. Obtained microgels can be stimulated by changes in the environment temperature as well as by the repulsion/attraction forces within polymeric network due to the reversible oxidation/reduction of the conjugated polymer. Microgels with unique properties can be operated in colloidal systems or used as building blocks for the preparation of nanostructured films.

     

N‐vinylcaprolactam‐based microgels: Synthesis and characterization

Poly(N‐vinylcaprolactam) (PVCL) is well known for its thermoresponsive behavior in aqueous solutions. PVCL combines useful and important properties; it is biocompatible polymer with the phase transition in the region of physiological temperature (32–38 °C). This combination of properties allows consideration of PVCL as a material for design biomedical devices and use in drug delivery systems. In this work, PVCL based temperature‐sensitive crosslinked particles (microgels) were synthesized in a batch reactor to analyze the effect of the crosslinker, initiator, surfactant, temperature, and VCL concentration on polymerization process and final microgels characteristics. The mean particle diameters at different temperatures and the volume phase‐transition temperature of the final product were analyzed. To obtain information about the inner structure of microgel particles, semicontinuous polymerizations were carried out and the evolution of the hydrodynamic average particle diameters at different temperatures of the microgel synthesized was investigated. In the case of microgel particles obtained in a batch reactor the size and the swelling‐de‐swelling behavior as a function of the temperature of the medium can be tuned by modulating the reaction variables. When the microgel particles were synthesized in a semibatch reactor different swelling‐de‐swelling behaviors were observed depending on particles inner structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2510–2524, 2008     

One‐Pot Four‐Component Synthesis of Tetrasubstituted Pyrroles

A convenient one‐pot four‐component synthesis of tetrasubstituted pyrroles was carried out through the reaction of butane‐2,3‐dione with α‐aminophosphorous ylides, obtained in situ from the 1 : 1 : 1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylate, and ammonium acetate.     

Metal‐Assisted One‐Pot Synthesis of Isoporphyrin Complexes

Zinc and cadmium complexes of meso‐arylisoporphyrins carrying a pyrrolyl or dipyrrinyl substituent at the sp³ carbon atom were obtained through a simple one‐pot variation of the Alder–Longo porphyrin synthesis. Key to the formation and stabilization of isoporphyrins is the presence of metal acetates during the oxidative macrocyclization step. The characteristic Q‐bands of isoporphyrins are found in the NIR region between 750 nm and 880 nm. All of the isolated pyrrolyl‐ and dipyrrinyl‐appended isoporphyrins are stable under typical laboratory conditions and allow chemical transformations like BF₂ coordination, transmetalation, and ligand exchange.     

Facile Synthesis of Well‐Defined Branched Sulfur‐Containing Copolymers: One‐Pot Copolymerization of Carbonyl Sulfide and Epoxide

Topological polymers possess many advantages over linear polymers. However, when it comes to the poly(monothiocarbonate)s, no topological polymers have been reported. Described herein is a facile and efficient approach for synthesizing well‐defined branched poly(monothiocarbonate)s in a “grafting through” manner by copolymerizing carbonyl sulfide (COS) with epichlorohydrin (ECH), where the side‐chain forms in situ. The lengths of the side‐chains are tunable based on reaction temperatures. More importantly, enhancement in thermal properties of the branched copolymer was observed, as the T_g value increased by 22 °C, compared to the linear analogues. When chiral ECH was utilized, semicrystalline branched poly(monothiocarbonate)s were accessible with a T_m value of 112 °C, which is 40 °C higher than that of the corresponding linear poly(monothiocarbonate)s. The strategy presented herein for synthesizing branched polymers provides efficient and concise access to topological polymers.     

One‐Pot Synthesis of Highly Emissive Dipyridinium Dihydrohelicenes

Condensation of a pyridyl‐2‐carbaldehyde derivative with 2‐(bromoethyl)amine hydrobromide gave tetracyclic pyrido[1,2‐a]pyrido[1′,2′:3,4]imidazo‐[2,1‐c]‐6,7‐dihydropyrazinium dications in excellent yields. Crystal structures and NOE data demonstrated the helical character of the dications, the dihedral angles between the two pyrido groups ranging from 28–45°. An intermediate in the synthesis was also characterized. A much brighter emission compared to literature helicenes has been found, with quantum yields as high as 60 % in the range of λ=460–600 nm. Preliminary cytotoxicity studies against HT‐29 cancer cells demonstrated moderate‐to‐good activity, with IC₅₀ values 12–30× that of cisplatin.     

Zirconium/Nickel‐Mediated One‐Pot Ketone Synthesis

A zirconium/nickel‐mediated one‐pot synthesis of ketones is reported. In the presence of Zn or Mn, Cp₂ZrCl₂ was found to dramatically accelerate the coupling and suppress side product formation via an I→SPy displacement at the same time. Unlike Zn/Pd‐ and Fe/Cu‐mediated one‐pot ketone syntheses, the new method is effective for nucleophiles bearing OR or equivalent functional groups at the α‐position. A mechanism comprising a nickel catalytic cycle, a zirconium catalytic cycle, and Zr→Ni transmetalation is proposed, and Cp₂ZrCl₂ and/or low‐valent Zr species are suggested to play crucial dual roles.     

A Novel One‐Pot Synthesis of Substituted Quinolines

A synthesis of quinoline derivatives is described via reaction between ethyl bromopyruvate (=ethyl 3‐bromo‐2‐oxopropanoate), acetylenedicarboxylate, and isatin (=1H‐indole‐2,3‐dione) in the presence of NaH as a base. Also, these reactions were performed without ethyl bromopyruvate. The reaction in the presence of ethyl bromopyruvate provides regioselectively a quinoline with the ethyl ester group in 4‐position. In the absence of ethyl bromopyruvate, the reaction leads to functionalized quinolines with the same ester groups in 2‐, 3‐, and 4‐positions.     

An Efficient One‐Pot Synthesis of Bis Butenolides

3,3′,4,4′‐Tetramethyl‐5,5′‐dioxo‐2,2′‐bifuran‐2,2′(5H,5′H) diyl diacetate was obtained from the reaction between 2,3‐dimethyl maleic anhydride and acetic anhydride in the presence of zinc in toluene. This easy synthetic route gave bis butenolide in excellent yield.