Hydrosilylation of unsaturated carbon-carbon bonds with hydrosilanes is a very important process to access organosilicon compounds and ranks as one of the most fundamental reactions in organic ...chemistry. However, catalytic asymmetric hydrosilylation of activated alkenes and internal alkenes has proven elusive, due to competing reduction of carbon-carbon double bond or isomerization processes. Herein, we report a highly enantioselective Si-C coupling by hydrosilylation of carbonyl-activated alkenes using a palladium catalyst with a chiral TADDOL-derived phosphoramidite ligand, which inhibits O-hydrosilylation/olefin reduction. The stereospecific Si-C coupling/hydrosilylation of maleimides affords a series of silyl succinimides with up to 99% yield, >99:1 diastereoselectivity and >99:1 enantioselectivity. The high degree of stereoselectivity exerts remote control of axial chirality, leading to functionalized, axially chiral succinimides which are versatile building blocks. The product utility is highlighted by the enantioselective construction of N-heterocycles bearing up to three stereocenters.
A highly efficient electrochemical reduction of 60fullerene-fused lactones to 60fullerene-fused ketones, a formal process of retro Baeyer-Villiger reaction, has been achieved for the first time. The ...electrochemically generated dianionic 60fullerene-fused lactones can be transformed into 60fullerene-fused ketones in the presence of acetic acid in 85-91% yields. Control experiments have been performed to elucidate the reaction mechanism. The products have been characterized with spectroscopic data and single-crystal X-ray analysis. Moreover, the electrochemical properties have also been investigated.
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IJS, KILJ, NUK, UL, UM, UPUK
Simultaneous electrochemical ring contraction and expansion reactions remain unexplored to date. Herein, the reductive electrosynthesis of heterocycle‐fused fulleroids from ...fullerotetrahydropyridazines and electrophiles in the presence of a trace amount of oxygen has been achieved with concurrent ring contraction and ring expansion. When trifluoroacetic acid and alkyl bromides are employed as electrophiles, heterocycle‐fused fulleroids with a 1,1,2,6‐configuration are regioselectively formed. In contrast, heterocycle‐fused fulleroids with a 1,1,4,6‐configuration are regioselectively produced as two separable stereoisomers if phthaloyl chloride is used as the electrophile. The reaction proceeds through multiple steps of electroreduction, heterocycle ring‐opening, oxygen oxidation, heterocycle contraction, fullerene cage expansion, and nucleophilic addition. The structures of these fulleroids have been determined by spectroscopic data and single‐crystal X‐ray diffraction analyses. The observed high regioselectivities have been rationalized by theoretical calculations. Representative fulleroids have been applied in organic solar cells as the third component and exhibit good performance.
The electrochemically triggered simultaneous ring contraction and expansion reaction of fullerotetrahydropyridazines with electrophiles in the presence of a trace amount of oxygen affords pyrazoline‐fused fulleroids with unprecedented 1,1,2,6‐ or 1,1,4,6‐addition patterns.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Endohedral clusterfullerenes exhibit unique chemical properties due to intramolecular electron transfer of the encaged metal cluster to the outer fullerene cages. We report the synthesis of two ...Sc3N@D3h‐C78 monoadducts 2 a and 2 b through the 1,3‐dipolar reaction of Sc3N@D3h‐C78 with carbonyl ylide bearing anomalous cis‐conformation regioselectivity. The molecular structures of these monoadducts are unambiguously confirmed by single‐crystal X‐ray crystallography, revealing that both 2 a and 2 b have cis‐conformations with the furan moiety grafted via 6,6‐closed addition patterns. Under the same conditions, the control reaction of C60 with carbonyl ylide affords two monoadducts 3 a and 3 b, which exhibit cis‐ and trans‐conformations, respectively, with 6,6‐closed addition patterns. According to theoretical calculations, the exclusive formation of the cis‐only Sc3N@D3h‐C78 monoadducts is a consequence of conjunct effects of thermodynamic stability of adducts, the reactivity of the addition site, and the cis‐dipole intermediate from trans 1.
Sc3N@D3h‐C78 was reacted with carbonyl ylide to form two isomeric monoadducts 2 a and 2 b bearing anomalous cis‐conformation regioselectivity and a 6,6‐closed addition pattern. Whereas isomeric monoadducts 3 a and 3 b with cis‐ and trans‐conformations were produced simultaneously for C60 under the same conditions. Adduct stability, reactivity of the addition site, and the nature of intermediates play a role in the different regioselectivity.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The direct decarboxylative meta-selective C–H acylation of a wide range of arenes is established via the ruthenium-catalyzed ortho-metalation strategy. This procedure, using Ru3(CO)12 as the catalyst ...and α-oxocarboxylic acids as the acylation source, featured broad substrate scope, good functional group tolerance, and high regioselectivity. Mechanistic studies demonstrated that a radical process and an 18e-octahedral ruthenium species were involved in this reaction. The present work provides a new strategy for the regioselective meta-acylation reactions and will be a powerful tool for the development of pharmaceutical and materials science.
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IJS, KILJ, NUK, PNG, UL, UM
Flexible supercapacitors have recently attracted intense interest. However, achieving high energy density via practical materials and synthetic techniques is a major challenge. Here, we develop a ...hetero-structured material made of black phosphorous that is chemically bridged with carbon nanotubes. Using a microfluidic-spinning technique, the hybrid black phosphorous-carbon nanotubes are further assembled into non-woven fibre fabrics that deliver high performance as supercapacitor electrodes. The flexible supercapacitor exhibits high energy density (96.5 mW h cm
), large volumetric capacitance (308.7 F cm
), long cycle stability and durability upon deformation. The key to performance lies in the open two-dimensional structure of the black phosphorous/carbon nanotubes, plentiful channels (pores <1 nm), enhanced conduction, and mechanical stability as well as fast ion transport and ion flooding. Benefiting from this design, high-energy flexible supercapacitors can power various electronics (e.g., light emitting diodes, smart watches and displays). Such designs may guide the development of next-generation wearable electronics.
•A hydrogel developed with fusiform-like ZnO(brZnO) and carboxymethyl chitosan.•The brZnO works both as crosslinker and nano-filler in the construction of hydrogel.•The hydrogel displays ...bidirectional sol–gel conversions at 42 °C and 26 °C.•The hydrogel possesses excellent injectability, self-healing, antibacterial activity.•The hydrogel creates a sterilized micro-environment that promotes wound tissue repair.
Hydrogels have attracted extensive attention as wound dressing because they can provide a moist microenvironment to accelerate wound healing. However, simple physical coverage of wound cannot satisfy the complicated process of wound repair. Here, we report an injectable multifunctional hydrogel (CMCS-brZnO) synthesized by incorporating fusiform-like zinc oxide nanorods (brZnO) into carboxymethyl chitosan (CMCS), in which the brZnO works dually as crosslinker and nano-filler. The hydrogel possesses controllable gelation time, quick self-healing, good tissue adhesion and fast hemostasis capability. Further, the CMCS-brZnO hydrogel presents excellent antibacterial properties with minimal inhibitory concentration (MIC) for E.coli and S.aureus of 0.0125 and 0.025 mg mL-1, respectively. The hydrogel could be injected directly into the irregular-shaped wounds in a full-thickness skin defect experiment, and the good fitting of the gel to the wound geometries together with the slow and sustainable release of antibacterial Zn2+ significantly promoted wound healing and reduced the inflammatory response. This study illustrates that the CMCS-brZnO hydrogels with an organic–inorganic micro-structure have great potential in accelerating wound healing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Herein, we report divergent additions of 2,2′‐diazidobiphenyls to C60 and Sc3N@Ih‐C80. In stark contrast to that of the previously reported bis‐azide additions, the unexpected cascade reaction leads ...to the dearomative formation of azafulleroids 2 fused with a 7‐6‐5‐membered ring system in the case of C60. In contrast, the corresponding reaction with Sc3N@Ih‐C80 switches to the C−H insertion pathway, thereby resulting in multiple isomers, including a carbazole‐derived 6,6‐azametallofulleroid 3 and a 5,6‐azametallofulleroid 4 and an unusual 1,2,3,6‐tetrahydropyrrolo3,2‐ccarbazole‐derived metallofullerene 5, whose molecular structures have been unambiguously determined by single‐crystal X‐ray diffraction analyses. Among them, the addition type of 5 is observed for the first time in all reported additions of azides to fullerenes. Furthermore, unexpected isomerizations from 3 to 5 and from 4 to 5 have been discovered, providing the first examples of the isomerization of an azafulleroid to a carbazole‐derived fullerene rather than an aziridinofullerene. In particular, the isomerism of the 5,6‐isomer 4 to the 5,6‐isomer 5 is unprecedented in fullerene chemistry, contradicting the present understanding that isomerization generally occurs between 5,6‐ and 6,6‐isomers. Control experiments have been carried out to rationalize the reaction mechanism. Furthermore, representative azafulleroids have been applied in organic solar cells, thereby resulting in improved power conversion efficiencies.
Divergent reactivities of 2,2′‐diazidobiphenyls toward C60 and Sc3N@Ih‐C80 have been disclosed. In the case of C60, a dearomative cascade reaction results in the formation of azafulleroids fused with a 7‐6‐5‐membered ring system, whereas Sc3N@Ih‐C80 undergoes a C−H insertion pathway, with the generation of carbazole‐derived 6,6‐ and 5,6‐azametallofulleroids and an unusual 1,2,3,6‐tetrahydropyrrolo3,2‐ccarbazole‐derived metallofullerene.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The solvent-free mechanochemical reaction has aroused increasing interest among scientists. Mechanical ball-milling can implement reactions under mild conditions, shorten the reaction time, and ...improve the reaction efficiency. Particularly, the most attractive characteristic of mechanochemistry is that it can alter the reaction pathway. However, few such examples have been reported so far. In this paper, we report the reaction of aldoximes with NaCl and Oxone under ball-milling conditions to afford
-acyloxyimidoyl chlorides, which are different from those of the liquid-phase counterpart.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Six chitosans with molecular weights ranging from 3.3 to 300kDa were prepared.•Combined effects of chitosan MW, temperature, pH on bacterial growth were studied.•The pH effects on water solubility ...and zeta potential of chitosans were examined.•Positive correlation between chitosan ZP and antibacterial activity was obtained.
Six chitosans with molecular weights (MWs) of 300, 156, 72.1, 29.2, 7.1, and 3.3kDa were prepared by cellulase degradation of chitosan (300kDa) and ultrafiltration techniques. We examined the correlation between activity against Escherichia coli and Staphylococcus aureus and chitosan MW, and provided the underlying explanation. In acidic pH conditions, the chitosan activity increased with increasing MW, irrespective of the temperature and bacteria tested. However, at neutral pH, chitosan activity increased as the MW decreased, and little activity was observed for chitosans with MW >29.2kDa. At pH 5.0 and 6.0, chitosans exhibited good water solubility and zeta potential (ZP) decreased with the MW, whereas the solubility and ZP of the chitosans decreased with increasing MW at pH 7.0. Particularly, low solubility and negative ZP values were determined for chitosans with MW >29.2kDa, which may explain the loss of their antibacterial activity at pH 7.0.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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