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Previously, we developed a gold-catalyzed cycloisomerization of dienediynes to synthesize the fused 6,7,5-tricyclic compounds. This reaction involves aliphatic C-H functionalization under mild conditions with high regio- and diastereoselectivities. Herein, we present a combined density functional theory (DFT) and experimental study to understand its mechanism. The reaction starts with a 6-endo-dig cyclization to generate a cis-1-alkynyl-2-alkenylcyclopropane. Then, a Cope rearrangement takes place to give a seven-membered-ring allene intermediate, whose central carbon atom possesses vinyl cation character and thus is highly reactive toward aliphatic C-H insertion. After the C-H insertion, two successive [1,2]-hydride shifts then occur to give the tricyclic product and to complete the catalytic cycle. Notably, steric effect induced by the bulky ligand is found to be important for the diastereocontrol in the C-H insertion step. DFT calculations suggested that the malonate-tethered substrate utilized in our previous work may undergo an undesired 5-exo-dig cyclization under gold catalysis, which could be the reason why the desired fused 6,7,5-tricarbocyclic product was not generated. These mechanistic insights then guided us to design substrates with a shortened carbon tether in the present work to inhibit the exo-dig cyclization so that the tandem cyclopropanation/Cope rearrangement/C-H functionalization could occur to construct polycarbocycles containing a seven-membered ring. This prediction was supported by new experiments, providing a new strategy to access fused 5,7,5-tricyclic and 5,7,6,6-tetracyclic carbocycles. In addition, how the substituents affect the chemoselectivity was also investigated.

A silver-catalyzed nitration/annulation of α-alkynyl arylols is reported by using tert-butyl nitrite (TBN) as a NO2 radical precursor, from which a set of 3-nitrated benzofurans were synthesized with moderate to good yields. This transformation initiated by an in situ generated NO2 radical proceeds efficiently under mild and neutral redox conditions, which provides a new pathway toward the 3-nitrobenzofuran framework via catalytic difunctionalization of internal alkynes.

Two neodymium β-diketonates metal-organic complexes, Nd(TTA)3TPTZ (1) and Nd(BFA)3TPTZ (2), have been synthesized by using two β-diketone ligands 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HTTA) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HFBA), and a macrocyclic conjugate ligand, 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ). The crystal structures of these two complexes were determined by single crystal X-ray diffraction. The X-ray diffraction analysis showed that each neodymium ion in the two complexes formed a Nine-Coordinated structure with six oxygen atoms of HTTA (or HBFA) ligands and three nitrogen atoms of TPTZ ligand by the characteristic of triclinic with P 1 ( — ) space group both. In the crystal structure of the two complexes, a very obvious aromatic donor-acceptor interaction can be observed between adjacent TPTZ ligand molecules, which play an important role in the formation of three-dimensional structures. The complexes were also characterized by infrared spectroscopy, elemental analysis, thermogravimetric and fluorescence spectra. Fluorescence analysis showed that the two complexes exhibited characteristic neodymium-centered emission due to the significant antenna effect of these ligands.

Summary Herein, we describe the protecting-group-free total synthesis of two structurally diverse Isodon diterpenoids, (+)-ent-kauradienone (3) and (−)-jungermannenone C (4), in 12 and 14 steps respectively, through sequential applications of three radical-based reactions, including the photoinduced skeletal rearrangements of bicyclo[3.2.1]octene ring systems. Further investigations of this photochemical radical rearrangement on a series of diverse terpenoids demonstrated both the unparalleled functional-group tolerance and the broad applicability of such late-stage photochemical rearrangements for the synthesis of structurally diverse and complex small molecules. Overall, the mild nature of late-stage photoinduced skeletal rearrangements might suggest that they are possible in a biological setting in unappreciated complimentary biosynthetic pathways.

Two new types of silver-catalyzed nitration–annulations of 2-alkynylanilines with tert-butyl nitrite (TBN) were reported, leading to the selective formation of a variety of nitrated indoles and indazole-2-oxides by changing the N-protection of 2-alkynylanilines. Ag-Catalyzed nitration–annulation of N-sulfonyl 2-alkynylanilines without C4 substituents afforded 5-nitroindoles under neutral-redox conditions, whereas the presence of C5 substituents gave 7-nitroindoles through silver catalysis. N-Methyl 2-alkynylanilines underwent a completely different process to furnish aroyl indazole-2-oxides.

Two neodymium(III) fluorou ternary complexes, [Nd(C5H2F6O2)3(C18H15OP)2] (C5H2F6O2 = hexafluoroacetylacetone, C18H15OP = triphenylphosphine oxide) (1) and [Nd(C5H2F6O2)3(C12H24N3O4P)2] (C5H2F6O2 = hexafluoroacetylacetone, C12H24N3O4P) = tri(4-morphollno) phosphine oxide) (2) have been synthesized by mild condition. The single crystals suitable for X-ray measurement were obtained and the structures of the two complexes were determined by X-ray diffraction in solid states. Single crystal analysis revealed that the two complexes were both eight-coordinated with one central Nd ion and eight O atoms from ligands. They were crystallized in monoclinic symmetry with P21/c and monoclinic symmetry C2/c space group, respectively. The complexes were characterized by IR-spectroscopy, thermogravimetric, elemental analyses and fluorescent. In fluorescence spectra, the two complexes both exhibit characteristic neodymium-centered emission.

A new sulfenylation reaction has been established, stereoselectively affording 37 examples of α-arylthio-α,β-unsaturated ketones with generally good yields via a metal-free three-component reaction of α-thiocyanate ketones with diaryliodonium salts and 1,2-dicarbonyls. The reaction enabled multiple bond-forming events including C(sp2)–S formation to provide a high-efficient and practical method toward α-arylthio-α,β-unsaturated ketones. The reasonable mechanism for forming α-arylthio-α,β-unsaturated ketones was proposed.

Gel breaker is one of the important factors affecting the effect of fracturing fluid flowing back and the enhancement of oil recovery. The Enzyme breaker can break the fracturing fluid quickly and completely, so that it can reduce the formation damage caused by the fracturing fluid. In this paper, the tolerance of enzyme produced by Bacillus amyloliquefaciens was evaluated to determine its feasibility as enzyme breaker. The study contained: 1. The preparation of the enzyme produced by Bacillus amyloliquefaciens. 2. The enzyme ability to reduce fracturing fluid viscosity was tested. 3. The residual enzyme activity at different pH, different temperature were valued by DNS method. The experimental results showed that: 1. the enzyme is suitable for neutral and acid environment, and it is not inactivated for 1 h in buffer of pH 5; it is resistant to medium and low temperature, and is not inactivated at 50 ℃ for 1 h. The results provide preliminary exploration for the development of enzyme breakers obtained from the Bacillus amyloliquefaciens.

The launch velocity of the projectile in the inductive electromagnetic launcher is affected by many factors. In this paper, the outlet velocity of the projectile influenced by the driving current is studied deeply. A simulation model is established by the Ansoft Maxwell electromagnetic simulation software and the relevant parameters of the system are set. The outlet velocity of the projectile is simulated with the different capacitor voltages and pulse widths of driving current. It can be seen from simulation results that the capacitor voltage and the driving current width have enormous effects on outlet velocity and outlet time. So, a reasonable choice of the capacitor voltage and the pulse width of driving current can make the projectile obtain a best outlet velocity.

Catalytic inverse electron demand Diels-Alder (IEDDA) reactions of heterocyclic aza-dienes are rarely reported since highly reactive and electron-rich dienophiles are often found not compatible with strong acids such as Lewis acids. Herein, we disclose that TFA-catalyzed reactions of electron-deficient 1,3,5-triazines and electron-deficient aldehydes/ketones can take place. These reactions led to highly functionalized pyrimidines as products in fair to good yields. The reaction mechanism was carefully studied by the combination of experimental and computational studies. The reactions involve a cascade of stepwise inverse electron demand hetero-Diels-Alder (ihDA) reactions, followed by retro-Diels-Alder (rDA) reactions and elimination of water. An acid was required for both ihDA and rDA reactions. This mechanism was further verified by comparing the relative reactivity of aldehydes/ketones and their corresponding vinyl ethers in the current reaction system.

A new silver-mediated 5-exo-dig cyclization of 2-alkynylbenzonitriles with disubstituted phosphine oxide and H2O has been developed. The reaction enables multiple bond-forming events including C–P, C–C and C–O bonds under atmospheric conditions, leading to the concise and direct formation of 28 examples of phosphorus-containing 1-indenones with generally good yields.

A chiral phosphoric acid-catalyzed Friedel–Crafts alkylation of o -hydroxybenzyl alcohols with 3-alkylindoles has been established, which was used to construct a biologically important diarylindol-2-ylmethane scaffold in high yields and with good enantioselectivities (up to 99% yield, 90:10 er ). Moreover, these novel compounds were subjected to tests to determine the in vitro cytotoxicity against carcinoma Hela cells. Nearly all of the tested compounds exhibited strong or moderate cytotoxicity to Hela cells with IC 50 values ranging from 6.821 to 28.042 μg/mL.

The dispersion accommodation technique based on defect layer are reported direct against the large positive dispersion of hollow single-mode Bragg fiber at $1.55\ \mu \text{m}$ which can increase the potential of hollow single-mode Bragg fiber in applications. First, the interaction between defect mode and fundamental mode are analyzed by using the optical software FDTD Solutions. Then, a comparative study on the dispersion curves of hollow single-mode Bragg fiber with and without defect layer is done. And then, the defect layers with different parameters are discussed separately. The simulation results show that by changing the refractive index, thickness and position of the defect layer, the fiber dispersion can be changed from zero to $7\times 10^{4} \text{ps} /(\text{nm}\cdot \text{km})$ . Finally the dispersion accommodations in hollow single-mode Bragg fiber based on defect layer are summarized.

Modes supported in air-core Bragg fibers with infinite number of H/L (high/low) layers are modeled and simulated which provide a solid foundation for the analysis of modes supported in air-core Bragg fibers with finite number of H/L layers. Three types of modes supported in Bragg fibers with a finite number of H/L layers are well defined and divided into branches in the mode spectrum. The three types of modes can be identified as quasi-guided modes, leaky modes and PML modes and their different characteristics are shown by the corresponding field patterns.

A highly efficient method for the synthesis of spiropyrazolone derivatives with structural diversity has been established via a facile three-component 1,3-dipolar cycloaddition of aldehydes, amino ester, and unsaturated pyrazolones. This protocol is applicable to a variety of unsaturated pyrazolones and aldehyde-derived azomethine ylides, providing an easy access to spiropyrazolone-based tetrahydro­pyrroles with structural diversity in high yields (up to 97%).

A novel organocatalytic asymmetric tandem Nazarov cyclization/semipinacol rearrangement reaction using "unactivated" substrates has been developed, generating a series of chiral spiro[4.4]nonane-1,6-diones in up to 96% yield and 97% enantiomeric excess. Significantly, it is the first direct example for asymmetric synthesis of cyclopentanones with four stereocenters using Nazarov cyclization. DFT calculations have been applied to understand the reaction mechanism, stereochemistry, and substituent effects.

A new sulfinate salt-mediated radical relay for the completion of C(sp3 )-H bond indenylation of cyclic ethers with readily available 2-alkynylbenzonitriles by combining silver/tert-butyl peroxide (TBHP) was established, providing a wide range of 3-alkylated 1-indenones with generally good yields. Interestingly, the current reaction system can tolerate an S-centered radical and a C-centered radical in one pot, in which the S-centered radical promotes the formation of the C-centered radical to induce a radical cascade without disturbing the reaction process. A reaction mechanism is also proposed based on control experiments.

Herein, we report a novel strategy based on a conformationally controlled RCM by a removable silyl group, which allows the facile synthesis of various bicyclo[n.3.1]alkenes, especially a set of highly strained bicyclo[5.3.1]alkenes. Further derivatizations of the silyl group and the resultant double bond of bicyclo[5.3.1]undecene 2 f enabled a concise synthesis of A-B-C ring skeleton of taxol. Density functional theory (DFT) calculations suggest that the introduction of a bulky silyl group at C-5 position of the 1,3-dialkenylcyclohexanol substrates dramatically lowers the energy bias gap between diaxial conformers (to RCM) and diequatorial conformers (to cross metathesis), thereby favoring the expected RCM reaction to give the challenging bridged molecules.

Intramolecular proton transfers are important processes in chemical reactions and biological transformations. In particular, the translocation of reactive carbanion centers can be achieved through 1,n-proton transfer in either a direct or an assisted manner (via the protonation/deprotonation mechanism). Despite some mechanistic investigations on proton transfers within zwitterionic species, no guiding principles have been summarized for carbanion-induced intramolecular proton transfers. Herein, we report our quantum chemical study on the carbanion translocations via intramolecular proton transfers. Our calculations indicated that the reaction barriers generally decrease with longer tether lengths and more π-withdrawing substituents. The physical bases behind these effects were revealed according to the charge and bond energy decomposition analysis, showing that the destabilizing closed-shell Pauli repulsions play important roles in determining the relative ease of intramolecular proton transfers. We also found that the thermodynamic driving force may affect the regiochemistry. This study may help chemists to understand whether a carbanion translocation occurs via an intramolecular proton transfer or with the assistance of proton shuttles, such as water and alcohols.

A novel gold(I)-catalyzed polycyclization of easily prepared linear dienediynes has been developed for the construction of fused 5,7,6-tricyclic ring systems in one step with high diastereocontrol. The polycyclization, a formal [4 + 3]/C-H activation reaction, takes place through gold(I)-catalyzed intramolecular cyclopropanation of diene with diyne, Cope rearrangement of cis-alkenylalkynylcyclopropane, aliphatic C-H activation via a seven-membered-ring allene intermediate, and [1,2]-H and -G (H or OAc) shifts.

Metal-free (5þ2) cycloadditions of homopyrrole and homofuran with dienophiles of N-phenylmaleimide, dimethyl acetylenedicarboxylate (DMAD), and maleic anhydride have been investigated by DFT calculations at the (U)B3LYP/6-31þG(d) level. Homopyrrole and homofuran act as 4-electron 1,5-dipoles in these (5þ2) reactions. These 1,5-dipoles can exist only in the transition states and undergo competitive concerted or stepwise (5þ2) cycloadditions. The (5þ2) cycloadditions of homopyrrole with dienophiles are stepwise involving generation of diradical intermediates, and its concerted pathways are disfavored marginally. In contrast, the (5þ2) cycloaddition of homofuran with maleic anhydride occurs in a concerted fashion, which is preferred over the stepwise diradical pathway slightly. The distortion energies from homopyrrole and homofuran to their respective 1,5-dipoles in the transition states are not high and this is the main reason why homopyrrole and homofuran can undergo metal-free (5þ2) cycloadditions with dienophiles. 2013 Published by Elsevier Ltd.

A highly efficient method for the synthesis of spiropyrazolone derivatives with structural diversity has been established via a facile three-component 1,3-dipolar cycloaddition of aldehydes, amino ester, and unsaturated pyrazolones. This protocol is applicable to a variety of unsaturated pyrazolones and aldehyde-derived azomethine ylides, providing an easy access to spiropyrazolone-based tetrahydro­pyrroles with structural diversity in high yields (up to 97%).

Reported is the first scalable synthesis of rac-jungermannenones B and C starting from the commercially available and inexpensive geraniol in 10 and 9 steps, respectively. The unique jungermannenone framework is rapidly assembled by an unprecedented regioselective 1,6-dienyne reductive cyclization reaction which proceeds through a vinyl radical cyclization/allylic radical isomerization mechanism. DFT calculations explain the high regioselectivity observed in the 1,6-dienyne reductive radical cyclization.

In this paper, carbon materials with solid and hollow sphere morphologies, have been prepared by reduction of hexachlorobenzene with metallic sodium at temperatures of 400-500°C for 6-10h. Characterized by XRD, TEM, SAED and Raman spectrum, the composition and morphology of the products are confirmed. The possible formation mechanism has also been proposed.

Nanocrystalline CuO with shuttle-morphology has been prepared conventionally by a microwave irradiation heating technique from an aqueous system in the presence of Cu(CH3COO)2• H2O and NaOH at room temperature. The X-ray powder diffraction pattern indicates that the product is indicated that the product was pure monoclinic phase of CuO. Further characterized by transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy and Raman spectra, the component of the products were confirmed.

Reported is the first scalable synthesis of rac-jungermannenones B and C starting from the commercially available and inexpensive geraniol in 10 and 9 steps, respectively. The unique jungermannenone framework is rapidly assembled by an unprecedented regioselective 1,6-dienyne reductive cyclization reaction which proceeds through a vinyl radical cyclization/allylic radical isomerization mechanism. DFT calculations explain the high regioselectivity observed in the 1,6-dienyne reductive radical cyclization.

A novel organocatalytic asymmetric tandem Nazarov cyclization/semipinacol rearrangement reaction using "unactivated" substrates has been developed, generating a series of chiral spiro[4.4]nonane-1,6-diones in up to 96% yield and 97% enantiomeric excess. Significantly, it is the first direct example for asymmetric synthesis of cyclopentanones with four stereocenters using Nazarov cyclization. DFT calculations have been applied to understand the reaction mechanism, stereochemistry, and substituent effects.

The presented step-economic synthesis of complex molecules proceeds with moderate to excellent diastereoselectivity.

New-type metallic oxide (M 2 O 3 M = Cr, Al) doped plastic shells used for inertial confinement fusion experiments are fabricated with emulsion techniques. Three different phases of solution (Wj, O, and W 2 ) are adopted for the fabrication process. The W 1 phase is 1 wt% of sodium lauryl sulfate in water. The W 1 phase solution is mixed with a 3 wt% M 2 O 3 -PS solution in benzenedichloroethane (O phase) while stirring. The mixed emulsion (W 1 /O) is then poured into a 3 wt% aqueous polyvinyl alcohol solution (W 2 phase) while stirring. The resulting emulsion (W 1 /O/W 2 ) is heated to evaporate benzene and dichloroethane, and thus, a solid M 2 O 3 -PS shell is formed. The diameter and wall thickness of the shells are 300 and 5 μm, respectively. The average surface roughness of the final products is

A series of ethyl 4-aryl-6-methyl-1,2,3,4-tetrahydropyrimidin-2-one-5-carboxylates 4 were synthesized by the condensation of aromatic aldehydes, ethyl acetoacetate and urea in the presence of ferric chloride hexahydrate under microwave irradiation. The reactions were completed in 4–6 min with 87–92% yield.

A series of hexahydrocoumarins 4 were synthesized by the reaction of aromatic aldehyde, 5,5-dimethyl-1,3-cyclohexandione and meldiums acid under microwave irradiation without catalyst. The structure of 4a was determined by x-ray analysis.

One mild multiple emulsions was used for the fabrication of hollow polystyrene (PS) spheres. Polystyrene was dissolved in a volatile organic solvent to form the O phase, then an aqueous phase containing a surfactant was transferred into above phase to form an oil-in-water (W in /O) emulsion, followed by addition of W in /O emulsion in the external W out phase, and solvent evaporation. Final product with diameter of 150 μm, surface roughness of 30 nm, and sphericity of 98.0% was obtained. The possible influences on the formation of PS hollow sphere were also discussed.

Nanocrystalline cobalt boride (Co2B) has been successfully synthesized by the reaction of CoCl2 with NaBH4 in the temperature range of 500–600°C in an autoclave. Characterized by X-ray powder diffraction (XRD), transmission electron micrographs (TEM), and Raman spectra, the composition and morphology of the products were confirmed. The mechanism for the formation of crystalline Co2B was proposed. This work contributes one facile method for preparing metallic borides.

Carbon hollow spheres were prepared at temperatures of 400 °C by the reaction reduction of hexachlorobenzene with metallic sodium. Characterized by XRD, TEM, SAED and Raman spectrum to confirm the composition and morphology of the products are confirmed. The possible formation mechanism was also proposed.

A type of iron (III) oxide doped plastic shell used for inertial confinement fusion experiments has been fabricated by emulsion techniques. Three different phases of solution (W1, O, and W2) are used for the fabrication process. The W1 phase is a 1 wt % of sodium lauryl sulfate in water. This W1 phase solution is mixed with a 3 wt % Fe2O3–polystyrene (PS) solution in benzene-dichloroethane (O phase) while stirring. The resulting emulsion (W1/O) is poured into a 3 wt % aqueous polyvinyl alcohol solution (W2 phase) while stirring. The resulting emulsion (W1/O/W2) is then heated to evaporate benzene and dichloroethane, and thus a solid Fe2O3–PS shell is formed. The diameter and wall thickness of the shells range from 150 to 500 μm and 5 to 15 μm, respectively. The average surface roughness of the shells is 40 nm, similar to that of the usual PS shells.A type of iron (III) oxide doped plastic shell used for inertial confinement fusion experiments has been fabricated by emulsion techniques. Three different phases of solution (W1, O, and W2) are used for the fabrication process. The W1 phase is a 1 wt % of sodium lauryl sulfate in water. This W1 phase solution is mixed with a 3 wt % Fe2O3–polystyrene (PS) solution in benzene-dichloroethane (O phase) while stirring. The resulting emulsion (W1/O) is poured into a 3 wt % aqueous polyvinyl alcohol solution (W2 phase) while stirring. The resulting emulsion (W1/O/W2) is then heated to evaporate benzene and dichloroethane, and thus a solid Fe2O3–PS shell is formed. The diameter and wall thickness of the shells range from 150 to 500 μm and 5 to 15 μm, respectively. The average surface roughness of the shells is 40 nm, similar to that of the usual PS shells.

A series of hexahydrocoumarins 4 were synthesized by the reaction of aromatic aldehyde, 5,5-dimethyl-1,3-cyclohexandione and meldiums acid under microwave irradiation without catalyst. The structure of 4a was determined by x-ray analysis.

A series of ethyl 4-aryl-6-methyl-1,2,3,4-tetrahydropyrimidin-2-one-5-carboxylates 4 were synthesized by the condensation of aromatic aldehydes, ethyl acetoacetate and urea in the presence of ferric chloride hexahydrate under microwave irradiation. The reactions were completed in 4–6 min with 87–92% yield.

C22H26N4O5, triclinic, P1̄ (no. 2), a = 8.4753(6) Å, b = 9.5662(7) Å, c = 14.479(1) Å, α = 101.674(4)°, β = 93.813(4)°, γ= 104.676(4)°, V = 1103.5 Å3, Z = 2, Rgt(F) = 0.0581, wRref(F2) = 0.1863, T = 296 K.

There are two molecules in the asymmetric unit of the title compound, C17H15ClO4, in which the dihedral angles between the five-membered rings are 57.3 (1) and 51.4 (1)°. An intramolecular O—H...O hydrogen bond occurs in each molecule. In the crystal, O—H...O and C—H...O hydrogen bonds link the moleclues into chains along the b axis.