Diels-Alder Addition of Dicyclopentadiene with Cyclopentadiene in Polar Solvents

Diels-Alder addition of dicyclopentadiene and cyclopentadiene in polar solvents has been studied to produce tricyclopentadiene（TCPD） that is a potential high-density fuel precursor. GC and MS analysis shows that the adducts contain two isomers, namely exo- and endo-TCPD. Theoretical simulation shows that although the transition state of endo-TCPD has a lower activation energy, exo-TCPD is thermodynamically preferred. Polar solvents can accelerate the reaction rate and improve the exo/endo ratio of TCPD because the transition state of exo-TCPD has a higher polarity than that of endo-TCPD. The solvent effect follows the order of polarity： benzyl methanol〉cyclohexanone〉toluene. The conversion rises when the temperature ranges from 120 to 150 ℃, but the selectivity of TCPD slightly decreases. Increasing the pressure can improve the conversion but the exo/endo ratio of TCPD is unchanged. The apparent kinetics in different solvents was determined via nonlinear regression. The activation energies are 99.47, 101.15, and 107.32 kJ/mol for benzyl methanol, cyclohexanone, and toluene, respectively. The optimal reaction conditions are as follows： benzyl methanol as solvent, temperature 150 ℃, and pressure 900 kPa. After an 11-hour reaction, a conversion of 58.0%, a TCPD selectivity of 95.7%, and an exo/endo ratio of 1/5.3 has been obtained.

Kinetics on Hydrogenation of Cyclopentadiene over Pd/γ-Al2O3 Catalyst

The macrokinetics of hydrogenation of cyclopentadiene was investigated over Pd/γ-Al2O3 catalyst.Experimental results showed that the relationship between the constituents and reaction time was in agreement with the characteristic of consecutive irreversible first-order reaction. Analysis on the reaction mechanism of selective hydrogenation of cyclopentadiene indicated that it is reasonable to express the hydrogenation rate of cyclopentadiene in the power law form. Parameters of the kinetic model were obtained by the Gauss-Newton method based on the experimental data. From the statistic test and residual error distribution the kinetic model was proved to be adequate.

Asymmetric Diels-Alder Reaction of 1-(S_R)-p-Tolylsulfinyl-3-penten-2-one with Cyclopentadiene Catalzed by a Chiral Titanium Reagent

Double asymmetric Diels-Alder reaction of 1(SR)-p-Tolylsulfinyl-3-penten-2-one with cyclopentadiene using a chiral titanium reagent was performed. The diastereoselectivity dependent on the size of aryl substituent involved in the chiral ligands was discussed Absolute configuration of the cycloadducts was conformed. Dramatic reversal of selectivity is observed.

MHEORETICAL STUDIES ON THE REACTION MECHANISMS OF CYCLOADDITION REACTIONS BETWEEN KETENE OR SUBSTITUTED KETENES AND CYCLOPENTADIENE

The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and ten transition states,corresponding to different approach geometries have been located and characterized,The regioselectivity and stereoselectivity of the reactions are correctly predicted by the calculations and the reaction mechanisms are analyzed in terms of electronic and steric effects of the substitutents on the reacting ketene and cyc-lopentadiene.

Metal-free multicomponent polymerization of activated diyne,electrophilic styrene and isocyanide towards highly substituted and functional poly(cyclopentadiene)

The development of a facile and efficient polymerization to prepare cyclopentadiene-containing polymers is of vital importance and highly desired. In this work, a metal-free multicomponent polymerization of activated diyne, electrophilic styrene and isocyanide for the preparation of highly substituted poly(cyclopentadiene) was established. Soluble and thermally stable polymers with high molecular weights are obtained in high yields under mild conditions. By introducing the tetraphenylethene or triphenylamine moiety into polymer backbones, the resultant polymers show unique aggregation-induced emission(AIE)characteristics. Interestingly, AIE polymers can also be generated in situ from non-AIE monomers. Moreover, the prepared polymers can generate photopatterns to function as photoresists and can also serve as visualizing agents to selectively stain the lipid droplets in live cells. This efficient polymerization will open up enormous opportunities for preparing functional cyclopentadiene-containing polymers applicable in diverse areas.

Characterization and reactivity of γ-Al_2O_3 supported Pd–Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene

Several γ-Al2O3 supported Pd-Ni bimetallic nanocatalysts （Pd-Ni （x：y）[Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively） were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd-NiJAl2O3 samples were confirmed to generate Pd-Ni bimetallic nanoparticles by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and transmission electron microscopy （TEM）. The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd-Ni （1：1 ）/Al2O3 （PN-1：1 ） catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.

Synthesis of 2-Acyl-2H-1,2,3-diazaphospholes and Their Diels-Alder Reaction with Cyclopentadiene

H-1,2,3-Diazaphospholes 3a3h were prepared from various ketone acylhydrazones and phosphorus trichlo-ride in the presence of triethylamine. Compounds 3 underwent feasible hetero-Diels-Alder reactions with cyclopen-tadiene to afford the respective anellated [1,2,3]diazaphospholes 4a4d as well as 4a'4d' in moderate yields. The endo rule in the reaction was observed under kinetic control conditions.

SYNTHESIS AND CHARACTERIZATION OF FLUORO-SUBSTITUTED β-ENAMINOKETONATO TITANIUM COMPLEXES AND THEIR CATALYTIC BEHAVIOR OF REGIOSELECTIVE ETHYLENE/CYCLOPENTADIENE COPOLYMERIZATION

The ethylene/cyclopentadiene （CPD） copolymerization behavior by using fluoro-substituted bis（fl- enaminoketonato） titanium complexes [FC6H4NC（CH3）CHCO（CF3）]2TiC12 （la-lc） has been investigated in detail. Upon utilizing MMAO as a cocatalyst, complexes la-lc exhibit high catalytic activities, affording the copolymers with high molecular weight and unimodal molecular weight distribution. Compared with non-substituted complex [C6HsNC（CH3）CHCO（CF3）]2TiC12 （1）, complexes la-lc can produce the copolymers with CPD incorporation adjusted in a wide range due to the enhancement of electrophilicity of metal center caused by introducing electron-withdrawing groups. Especially complex lc bearing fluorine at the para-position of N-aryl moiety provides the highest CPD incorporation, which is nearly two times （18.5 mol%） higher than the non-substituted complex 1 （8.9 mol%） under the same conditions. The highest CPD incorporation up to 24.6 mol% can be easily achieved using this complex. 1H-and 13C-NMR spectra demonstrate that these fluoro-substituted complexes possess regioselective nature with exclusive 1,2-insertion fashion, and alternating ethylene-CPD sequence can be detected at high CPD incorporation.

A New Synthetic Method of Highly Substituted Cyclopentadienes from α,β-Unsaturated Alkynones

Promoted by samarium diiodide in THF, the α,β-unsaturated alkynones were reduced to afford intermolecular reductive coupling products. The multiply substituted cyclopentadienes were prepared conveniently in good yields.

Synthesis of 5-vinyl-2-norbornene through Diels-Alder reaction of cyclopentadiene with 1,3-butadiene in supercritical carbon dioxide

An efficient method for the synthesis of 5-vinyl-2-norbornene from cyclopentadiene and 1,3-butadiene was developed.The Diels-Alder reaction of cyclopentadiene with 1,3-butadiene proceeded smoothly in supercritical carbon dioxide in the absence of any polymerization inhibitor to produce the corresponding5-vinyl-2-norbornene in satisfactory yield with high selectivity.

Synthesis,characterization and antioxidant activities of highly functionahzed cyclopentadienes catalyzed by ZnO-nanorod as economic and efficient heterogeneous nano catalyst

A three-component condensation was applied for the preparation of cyclopentadiene derivatives through the reaction of primary amines,alkyl propiolate and dialkyl acetylenedicarboxylate in the presence of catalytic amount of ZnO-nanorods（Zn-NR） under solvent-free conditions at 50 ℃.The method has proved to be synthetically green,simple,and effective with high atom economy and yield.The catalyst also revealed significant reusability.Moreover,the antioxidant activity and free radical scavenging capacity of the newly synthesized derivatives 4a,4b,4c,and 4d was screened using free radical scavenging 2,2-diphenyl-1-picrylhydrazyl（DPPH） and ferric reducing antioxidant power（FRAP）assays and compared with hydroxytoluene（BHT） and tert-butylhydroquinone（TBHQ）.These compounds do not exhibit good DPPH radical scavenging,but they have a desirable FRAP.

A new alkaloid from Castanea mollissima Blume

A new alkaloid, named 6-（2＇,3＇-dihydroxy-4＇-hydroxymethyl-tetrahydro-furan-1＇-yl）cyclopentadiene[c]pyrrole-1,3-diol, was isolated from the seeds of Castanea mollissima Blume. The structure was elucidated based on spectroscopic evidence including 2D NMR techniques.

Perspective on synthesis of high-energy-density fuels:From petroleum to coal-based pathway

High-energy–density(HED)fuel is specifically pivotal to improve the performance of volume-limited aircrafts.The widely used HED fuels composed of polycyclic hydrocarbons are mainly synthesized from petroleum feedstocks.In order to ensure abundant supply,alternative resources such as coal should be considered.Herein,we summarize the synthesis methods and properties of typical HED fuels by using petroleum-derived cyclopentadiene(CPD)as key feedstock through dimerization,cycloaddition,hydrogenation and isomerization/photoisomerization reactions,and then propose a blueprint for synthesizing HED fuels from coal.The method to produce CPD from coal is analyzed and feasibility is demonstrated according to theoretical calculations and reported results.This review provides a novel route for synthesis of HED fuels from coal.

MODIFICATION OF PALLADIUM METALLIC CATALYST WITH POLYMER-ANCHORED THIOETHER LIGANDS

A well-dispersed metallic palladium catalyst modified by polymer-anchored thioether ligands was used for the hydrogenation of cyclopentadiene to cyclopentene with high activity and selectivity in ambient condition. The evidences to show the modification of catalytic properties by polymer anchored ligands were given.

Aqueous Diels-Alder Reactions of Cyclopentadicnc with Symmetric Diester of Fumarate or Maleate

Symmetric, diesters of cis- or trans- bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylate were prepared by aqueous Diels-Alder reaction of cyclopentadiene with symmetric diester of fumarate or maleate.

Reaction of Arylnitroso Derivatives: Synthesis of Arylimino 2,5-Dihydrofuran and Arylamino Fulvenes Derivatives

Herein we report the reactivity of N-(2,4-dicyano-1,5-dimethyl-3-arylcyclopenta-2,4-dienyl)-2,2,2- trifluoroacetamides and N,N-dimethyl-4-nitrosoaniline which provide compounds derived from Ehrlich-Sachs condensation, dihydrofuran derivatives and fulvene derivatives by adjusting the reaction conditions.

Rh(III)-Catalyzed Enantioselective Intermolecular Aryl C—H Bond Addition to Aldehydes

The direct addition of aryl C—H bond to carbon-heteroatom double bond by transition-metal-catalyzed C—H activation has been extensively investigated in the past decade. However, the enantioselective intermolecular C—H addition to aldehyde has not yet been reported and is of significant challenge. Rh(III)-catalyzed highly enantioselective intermolecular C—H addition of aryl oxime ethers to glyoxylates is reported. Chiral mandelic acid esters were obtained in excellent yields (up to 98%) and enantioselectivity (up to 99% ee) in the presence of a chiral CpRh(III) catalyst under mild conditions. The substituents on the Cp ring and BINOL skeleton were responsible for the high enantioselectivity observed. The method displays a broad substrate scope and good functionality tolerance. These results provide not only a promising C—H addition approach but also a proof of concept for developing broader asymmetric C—H addition reactions.

EFFECTS OF CENTRAL METALS AND σ-LIGANDS IN 1,1'-TRIMETHYLENEDICY-CLOPENTADIENYL RARE EARTH(Ⅲ) COMPLEXES ON REDUCTION OF OLEFIN

Sodium hydride is widely used as Lewis base in organic syntheses, but cannot reduce the carbon-carbon double bond alone. Recently, we have found that tricyclopentadienyl rare earth complexes-sodium hydride systems are not only nice reducing-