Silyl‐Terminated Ethylene‐co‐Norbornene Copolymers by Organotitanium‐Based Catalysts

Ethylene (E) and norbornene (N) were copolymerized in the presence of PhSiH₃ as chain‐transfer agent with [Ti(η⁵:η¹‐C₅Me₄SiMe₂NBu^t)(η¹‐Me)₂] precatalyst combined with [Ph₃C][B(C₆F₅)₄]. The silane was introduced at chain‐ends of E‐co‐N copolymers with concomitant reinitiation of the growing polymer chain. The concentrations of the silane and polymer molecular weight are inversely correlated. The characteristic signals of  SiH₂Ph chain‐ends were observed by ¹H NMR. The Si heteroatom is predominantly adjacent to ethylene units in E‐co‐N copolymers with high N content.

     

Visible‐Light‐Induced Nickel‐Catalyzed Negishi Cross‐Couplings by Exogenous‐Photosensitizer‐Free Photocatalysis

The merging of photoredox and transition‐metal catalysis has become one of the most attractive approaches for carbon–carbon bond formation. Such reactions require the use of two organo‐transition‐metal species, one of which acts as a photosensitizer and the other one as a cross‐coupling catalyst. We report herein an exogenous‐photosensitizer‐free photocatalytic process for the formation of carbon–carbon bonds by direct acceleration of the well‐known nickel‐catalyzed Negishi cross‐coupling that is based on the use of two naturally abundant metals. This finding will open new avenues in cross‐coupling chemistry that involve the direct visible‐light absorption of organometallic catalytic complexes.     

Regio-and Stereo-selective Bioreduction of Diketo-n-butylphosphonate by Baker''''s Yeast

Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｂａｋｅｒ’ｓｙｅａｓｔ (Ｓａｃｃｈａｒｏｍｙｃｅｓｃｅｒｅｖｉｓｉａｅ)ｉｓｗｅｌｌｒｅｃｏｇｎｉｚｅｄａｓａｖａｌｕａｂｌｅｓｔｅｒｅｏｓｅｌｅｃｔｉｖｅｒｅａｇｅｎｔｉｎｂｉｏ ｔｒａｎｓｆｏｒｍａｔｉｏｎｓｏｆｏｒｇａｎｉｃｍｏｌｅｃｕｌｅｓ .Ｔｈｅａｓｙｍｍｅｔｒｉｃｒｅ ｄｕｃｔｉｏｎｏｆｃａｒｂｏｎｙｌｇｒｏｕｐｓｗｉｔｈｔｈｉｓｍｉｃｒｏｂｅｈａｓｂｅｅｎｓｔｕｄｉｅｄｅｘｔｅｎｓｉｖｅｌｙ .Ｍｏｒｅｏｖｅｒ,ｉｎｔｈｅｃｏｕｒｓｅｏｆｒｅｄｕｃｔｉｏｎｏ…     

Vesicles Formed by Oligostyrene‐block‐Oligoaniline‐block‐Oligostyrene Triblock Oligomer

Novel π‐conjugated coil–rod–coil triblock oligomers containing optoelectronic active oligoaniline segments were synthesized. The block oligomer can self‐assemble into diverse aggregating morphologies including spherical micelles and thin‐layer vesicles in THF, which is found associated with the removing of the protecting groups of oligoaniline segments. A possible mechanism was proposed to explain the self‐assembly behavior changes in which chain conformation variation of the aniline segments initiated from deprotection of the nitrogen atoms is pointed to be the key factor that dominates the transition process.

     

Pd‐Catalyzed Selective Bifunctionalization of 3‐Iodo‐o‐Carborane by Pd Migration

A palladium‐catalyzed highly selective 3,4‐bifunctionalization of 3‐I‐o‐carborane has been developed, leading to the preparation of 3‐alkenyl‐4‐R‐o‐carboranes (R=alkyl, alkynyl, aryl, allyl, CN, and amido) in high to excellent yields. This protocol combines the sequential activation of cage B(3)?I and B(4)?H bonds by Pd migration from exo‐alkenyl sp² C to cage B(4), which is driven by thermodynamic force. This represents a brand‐new strategy for selective bifunctionalization of carboranes with two different substituents.     

Oxazoline‐terminated macromonomers by the alkylation of 2‐methyl‐2‐oxazoline

Well‐defined macromonomers of poly(ethylene oxide) and poly(tert‐butyl methacrylate) were obtained by anionic polymerization induced directly by the carbanion issued from 2‐methyl‐2‐oxazoline. When ethylene oxide was added to this carbanion with lithium as the counterion, a new compound able to initiate the polymerization of ε‐caprolactone in an anionically coordinated way was synthesized, and this led to well‐defined poly(ε‐caprolactone) macromonomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2440–2447, 2005     

Synthesis of 1‐amino‐2‐methylindoline by Raschig process: Kinetics of the oxidation of 1‐amino‐2‐methylindoline by chloramine

The synthesis of 1‐amino‐2‐methylindoline by the Raschig process was undertaken in aqueous solution. The principal side reaction that occurs in the medium is the oxidation of 1‐amino‐2‐methylindoline formed by chloramine. To increase the yield of 1‐amino‐2‐methylindoline, its oxidation by chloramine was studied by GC and HPLC at various concentrations of reactants and for a pH interval ranging between 9.9 and 13.5. The reaction is bimolecular and exhibits a specific acid catalysis. In alkaline medium, 1‐amino‐2‐methylindole is the principal product. The enthalpy and entropy of activation were determined at pH 12.89. In unbuffered solution, the interaction was autocatalyzed by the ammonium ions formed, which indicates a competitive oxidation of neutral and ionic forms of 1‐amino‐2‐methylindoline by chloramine. A mathematical treatment based on one implicit equation allows a quantitative interpretation of all the phenomena observed over the above pH interval. It takes both acid–base dissociation equilibrium and alkaline hydrolysis of chloramine into account. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 515–523, 2002     

Separation of p‐Divinylbenzene by Selective Room‐Temperature Adsorption Inside Mg‐CUK‐1 Prepared by Aqueous Microwave Synthesis

A new Mg^II‐based version of the porous coordination polymer CUK‐1 with one‐dimensional pore structure was prepared by microwave synthesis in water. Mg‐CUK‐1 is moisture‐stable, thermally stable up to 500 °C, and shows unusual reversible soft‐crystal behavior: dehydrated single crystals of the material selectively adsorb a range of organic molecules at ambient temperature and pressure. Both polar and apolar aromatic compounds, including pyridine, benzene, p‐xylene, and p‐divinylbenzene (p‐DVB), are all readily adsorbed, while other isomers from complex mixtures of xylenes or DVBs are selectively excluded. The solvent‐loaded structures have been studied by single‐crystal X‐ray diffraction. Time‐dependent liquid sorption experiments using commercially available DVB demonstrate a high and rapid selective adsorption of p‐DVB and exclusion of m‐DVB and ethylvinylbenzene isomers.     

Enantioselective Visible‐Light‐Mediated Formation of 3‐Cyclopropylquinolones by Triplet‐Sensitized Deracemization

3‐Allyl‐substituted quinolones undergo a triplet‐sensitized di‐π‐methane rearrangement reaction to the corresponding 3‐cyclopropylquinolones upon irradiation with visible light (λ=420 nm). A chiral hydrogen‐bonding sensitizer (10 mol %) was shown to promote the reaction enantioselectively (88–96 % yield, 32–55 % ee). Surprisingly, it was found that the enantiodifferentiation does not occur at the state of initial product formation but that it is the result of a deracemization event. The individual parameters that control the distribution of enantiomers in the photostationary state have been identified.     

Analysis and Identification of the Chemical Constituents of Ding‐Zhi‐Xiao‐Wan Prescription by HPLC‐IT‐MSn and HPLC‐Q‐TOF‐MS

Ding‐Zhi‐Xiao‐Wan (DZXW) is a famous traditional Chinese medicine (TCM) formula, which is composed of four herbs, Ginseng Radix, Poria, Polygala Radix and Acori Tatarinowii Rhizoma. It has been popularly used for the treatment of emotional disease, like Alzheimer's disease, Parkinson's disease, depression, anxiety, forgetfulness and neurasthenia. In this research, a high‐performance liquid chromatography coupled with ion‐trap tandem mass spectrometry (HPLC‐IT‐MSⁿ) method along with a high‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry (HPLC‐Q‐TOF‐MS) method in negative ion mode was established to investigate the major constitutions in DZXW. The extracts were prepared by ultra‐sonication in ethyl acetate, n‐butanol, 95% ethanol and deionized water sequentially as well as in deionized water directly. A Kromasil C18 column was used to separate the extracts of DZXW. Acetonitrile and 0.1% aqueous formic acid (V/V) were used as the mobile phase. A total of 64 components were characterized, including 16 triterpenoids, 14 Polygala saponins, 10 oligosaccharide esters, 6 sucrose esters, 2 xanthone C‐glycosides and 16 ginsenosides.     

Luminescence Regulation of Silver‐Thiolate Clusters Protected by 1,2‐Dithiolate‐o‐carborane

Engineering the surface of the metal clusters with the core structure maintained and tuning their luminescence in a wide range is still a challenge in the nanomaterial research. We modified six mono‐pyridyl ligands with different electronic effects (conjugation effect or induction effect) on a superatomic silver cluster [Ag₁₄(C₂B₁₀H₁₀S₂)₆(CH₃CN)₈] (denoted as Ag₁₄) through in situ site‐specific surface engineering, and obtained the corresponding clusters [Ag₁₄(C₂B₁₀H₁₀S₂)₆(CH₃CN)₆(L₁/L₂)₂] (denoted as NC‐1, 2, L₁/L₂ = 4‐acetylpyridine/ 4‐carboxypyridine) and [Ag₁₄(C₂B₁₀H₁₀S₂)₆(L₃/L₄/L₅/L₆)₈] (denoted as NC‐3, 4, 5, 6, L₃/L₄/L₅/L₆ = 4‐phenylpyridine/4‐(1‐naphthyl)pyridine/9‐(4‐pyridine)anthracene/9‐(4‐pyridine)pyrene). Through the modification of the Ag₁₄ cluster, a wide‐range luminescence from blue to red was realized. This work might provide a practical guide for improving the emission performance of metal clusters via surface engineering.     

High‐Molecular‐Weight Polynucleotides by Transferase‐Catalyzed Living Chain‐Growth Polycondensation

We present terminal deoxynucleotidyl transferase‐catalyzed enzymatic polymerization (TcEP) for the template‐free synthesis of high‐molecular‐weight, single‐stranded DNA (ssDNA) and demonstrate that it proceeds by a living chain‐growth polycondensation mechanism. We show that the molecular weight of the reaction products is nearly monodisperse, and can be manipulated by the feed ratio of nucleotide (monomer) to oligonucleotide (initiator), as typically observed for living polymerization reactions. Understanding the synthesis mechanism and the reaction kinetics enables the rational, template‐free synthesis of ssDNA that can be used for a range of biomedical and nanotechnology applications.     

Near‐Infrared‐Light‐Driven Artificial Photosynthesis by Nanobiocatalytic Assemblies

Artificial photosynthesis in nanobiocatalytic assemblies aims to reconstruct man‐made photosensitizers, electron mediators, electron donors, and redox enzymes for solar synthesis of valuable chemicals through photochemical cofactor regeneration. Herein, we report, for the first time, on nanobiocatalytic artificial photosynthesis in near‐infrared (NIR) light, which constitutes over 46% of the solar energy. For NIR‐light‐driven photoenzymatic synthesis, we synthesized silica‐coated upconversion nanoparticles, Si‐NaYF4:Yb,Er and Si‐NaYF4:Yb,Tm, for efficient photon‐conversion through Förster resonance energy transfer (FRET) with rose bengal (RB), a photosensitizer. We observed NIR‐induced electron transfer by using linear sweep voltammetric analysis; this indicates that photoexcited electrons of RB/Si‐NaYF4:Yb,Er are transferred to NAD+ through a Rh‐based electron mediator. RB/Si‐NaYF4:Yb,Er nanoparticles, which exhibit higher FRET efficiency due to more spectral overlap than RB/Si‐NaYF4:Yb,Tm, perform much better in the photoenzymatic conversion.     

Biaryl Synthesis by Ring‐Opening Friedel–Crafts Arylation of 1,4‐Epoxy‐1,4‐dihydronaphthalenes Catalyzed by Iron Trichloride

Biaryl and heterobiaryl compounds are important frameworks across a range of fields including pharmaceutical and functional material chemistries. We have accomplished the efficient synthesis of various naphthalene‐linked arenes and heteroarenes as biaryls and heterobiaryls by the FeCl₃‐catalyzed Friedel‐Crafts reactions accompanied by the ring‐opening of the 1,4‐epoxy moiety of 1,4‐epoxy‐1,4‐dihydronaphthalenes. Especially, it is noteworthy that 1‐silylated substrates were regioselectively transformed to the 3‐aryl‐1‐silylnaphthalenes and the double Friedel–Crafts reactions using thiophene derivatives could directly produce the corresponding bis‐naphthlated thiophene derivatives.