Skeletal reorganization reactions have emerged as an intriguing tool for converting readily available compounds into complicated molecules inaccessible by traditional methods. Herein, we report a ...unique skeleton‐reorganizing coupling reaction of cycloheptatriene and cycloalkenones with amines. In the presence of Rh/acid catalysis, cycloheptatriene can selectively couple with anilines to deliver fused 1,2‐dihydroquinoline products. Mechanistic studies indicate that the retro‐Mannich type ring‐opening and subsequent intramolecular Povarov reaction account for the ring reorganization. Our mechanistic studies also revealed that skeleton‐reorganizing amination between anilines and cycloalkenones can be achieved with acid. The synthetic utilization of this skeleton‐reorganizing coupling reaction was showcased with a gram‐scale reaction, synthetic derivatizations, and the late‐stage modification of commercial drugs.
An unusual catalytic coupling reaction of cycloheptatriene and cycloalkenones with amines proceeds through a skeleton‐reorganization process for the selective synthesis of fused 1,2‐dihydroquinolines. Mechanistic studies indicate that the reactions proceed through a retro‐Mannich‐type ring‐opening and a subsequent intramolecular Povarov process.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Depending on the reactant property and reaction mechanism, one major regioisomer can be favored in a reaction that involves multiple active sites. Herein, an orthogonal regulation of nucleophilic and ...electrophilic sites in the regiodivergent hydroamination of isoprene with indazoles is demonstrated. Under Pd‐hydride catalysis, the 1,2‐ or 4,3‐insertion pathway with respect to the electrophilic sites on isoprene could be controlled by the choice of ligands. In terms of the nucleophilic sites on indazoles, the reaction occurs at either the N1‐ or N2‐position of indazoles is governed by the acid co‐catalysts. Preliminary experimental studies have been performed to rationalize the mechanism and regioselectivity. This study not only contributes a practical tool for selective functionalization of isoprene, but also provides a guide to manipulate the regioselectivity for the N‐functionalization of indazoles.
The Pd‐catalyzed regiodivergent coupling reactions between indazoles and isoprene have been developed through the orthogonal regulation of nucleophilic and electrophilic sites.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The catalytic bis‐allylation of alkynes is an important but challenging protocol to construct all‐carbon tetra‐substituted alkenes. Particularly, the catalytic unsymmetrical bis‐allylation of alkynes ...remains as an underexplored task to date. We herein report an unprecedented unsymmetrical bis‐allylation by simultaneously utilizing electrophilic trifluoromethyl alkene and nucleophilic allylboronate as the allylic reagents. With the aid of robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions. Mechanistic studies indicate that the reaction may proceed through a β‐fluorine elimination of a nickelacycle followed by a transmetalation step with allylboronate. The present method exhibits a good tolerance of various functional groups. Besides, the skipped triene products can undergo an array of elaborate transformations, which highlights the potential applications of this strategy.
An efficient unsymmetrical bis‐allylation of alkynes has been developed by simultaneously utilizing electrophilic trifluoromethyl alkenes and nucleophilic allylboronates as the allylic reagents. With the aid of a robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
To improve the interfacial properties between carbon fibers (CFs) and polycarbonate (PC) resin, multi-walled carbon nanotubes (MWCNTs) were deposited onto desized CF surfaces using an ...ultrasonic-assisted electrophoretic deposition method, forming a multi-scaled hierarchical structure. The results showed that morphologies and geometrical structures of the as-prepared hierarchical structures could be readily tailored by varying in length and concentration of the CNT suspension. The optimum conditions were determined to be CNT length of 1-5 μm with suspension concentration of 0.5–1 wt%. A post-treatment, in combination of a polymer binder and laser irradiation, was followed to solidify the morphology and geometry of the CNT network structures formed by the CNTs with length 1-5 μm, which allowed a 22.9% ± 1.6% improvement in the interfacial bonding strength than that without the post-treatment and 68.1% ± 2.3% improvement than bare CF, evaluated by a single-filament fragmentation test. It was the well-defined CNT porous network structures that are favorable for thermoplastic resin infiltration through channels for resin flow and capillary action, thus enhancing the composite interfacial properties.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
As a large number of organic compounds possessing two isoprene units, monoterpenes and monoterpenoids play important roles in pharmaceutical, cosmetic, agricultural, and food industries. In ...nature, monoterpenes are constructed from geranyl pyrophosphate (C10) via various transformations. Herein, the bulk C5 chemical—isoprene, is used for the creation of various monoterpenoids via a nucleophilic aromatization of monoterpenes under cascade catalysis of nickel and iodine. Drugs and oil mixtures from conifer and lemon can be convergently transformed to the desired monoterpenoid. Preliminary mechanistic studies are conducted to get insights about reaction pathway. Two types of cyclic monoterpenes can be respectively introduced onto two similar heterocycles via orthogonal C–H functionalization. And various hybrid terpenyl indoles are programmatically assembled from abundant C5 or C10 blocks. This work not only contributes a high chemo-, regio-, and redox-selective transformation of isoprene, but also provides a complementary approach for the creation of unnatural monoterpenoids.
Developing efficient strategies to realize divergent arylation of dienes has been a long-standing synthetic challenge. Herein, a nickel catalyzed divergent Mizoroki-Heck reaction of 1,3-dienes has ...been demonstrated through the regulation of ligands and additives. In the presence of Mn/NEt
, the Mizoroki-Heck reaction of dienes delivers linear products under Ni(dppe)Cl
catalysis in high regio- and stereoselectivities. With the help of catalytic amount of organoboron and NaF, the use of bulky ligand IPr diverts the selectivity from linear products to branched products. Highly aryl-substituted compounds can be transformed from dispersive Mizoroki-Heck products programmatically. Preliminary experimental studies are carried out to elucidate the role of additives.
The favorable interfacial properties of carbon fibers (CFs) and matrix are the key to the design and fabrication of a CF reinforced composite with superior micromechanical properties for various ...modern technological applications. However, high viscosity of a thermoplastic polymer makes resin infusion difficult, resulting in poor impregnation into CFs, ultimately leading to insufficient interfacial adhesion during composites fabrication process. Here the polycarbonate nanoparticles (PC-NPs) were pre-coated on the CFs from PC-NP aqueous solution and formed compact microstructure, which significantly improved the resin impregnation around CFs and interfacial adhesion between CFs and PC matrix. This PC-NP assisted CF/PC composite exhibits an increased interfacial shear strength up to 37.03 MPa, which is ~67.25% higher than that of un-coated CF/PC composite. Moreover, the tensile strength and flexural strength are enhanced remarkably by ~41.06% and ~22.16% increase, respectively. These results therefore demonstrate that the attachment of thermoplastic PC-NPs is a facile, environmental-friendly and viable approach in design and modification of the interfacial properties of CFs and PC matrix, which can be expanded for other multifunctional CF-reinforced composites with unique micromechanical properties for various practical applications.
•A controlled attachment of PC-NPs on CF surface can be achieved by electrostatic attraction in the aqueous solution.•PC-NPs attachment to the CF surface leads to high resin impregnation and a desired interface between CFs and PC matrix.•PC-NP assisted CF/PC composites exhibit highly efficient interfacial adhesion and excellent mechanical properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A regiospecific allyl-allyl coupling reaction between 1,3-dienes and allylboronates has been demonstrated under nickel catalysis. Salient features of this method include the earth-abundant metal ...catalyst, excellent regioselectivity and good functional group tolerance. Notably, even congested allyl substrates can also be applied to this protocol, thus allowing for the rapid preparation of a series of valuable 1,5-dienes.
A nickel-hydride catalysis has been developed to facilitate the allyl-allyl cross-coupling reactions between 1,3-dienes and allyl-B(pin) in excellent regioselectivity.
This study presents two methods of controlling neutral-point voltage oscillation in a hybrid VIENNA rectifier, which is composed of the parallel association of a three-phase single-switch Boost ...rectifier with a VIENNA-type rectifier. The neutral-point oscillation reason has been analysed with a mathematical model. Meanwhile, the two neutral-point control methods of a simplified method based on a zero-sequence component injection and a dual-carrier pulse-width modulation (PWM) method are proposed to control the voltage deviation of the split DC-link and three-time fundamental frequency neutral-point voltage fluctuation with a decrease from ±1.6 to ±1 V, respectively. Moreover, the significant oscillation in the neutral-point voltage caused by unbalanced loads or asymmetric capacitor parameters can also be effectively suppressed by using the dual-carrier PWM method. Furthermore, the performance comparison between these two methods is provided. The experimental results show that the system after being introduced the proposed two methods still exhibits a low-order input current harmonic such as second, third, and fourth harmonics as well as the input current total harmonic distortion is lower than the standard 5%.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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