- Ultrasmall and Stable Pd and Pt Nanoparticles Within Zeolite HY Through Impregnated Method with Enhanced Semihydrogenation Selectivity
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In this study, with zeolite HY as support, ultrasmall Pd and Pt nanoparticles were successfully immobilized into zeolite HY crystals through an optimized impregnation approach. The success of this new approach mainly relied on the selecting appropriate metal precursor to make Pd and Pt element exists with the cation forms, which can facilitate their diffusion into inner channels of zeolite HY through electrostatic attraction and capillary force. Integration of confinement effect of zeolite HY, taking zeolite HY (Si/Al = 3) encapsulation of ultrasmall Pd NPs (Pd@HY-3) as an instance, Pd@HY-3 catalyst exhibited enhanced catalytic selectivity in semihydrogenation of alkynes, in comparison with Pd/HY, Pd/C, Pd/Al2O3 and lindlar catalysts. This improved catalytic selectivity can be attributed to the constrained upright adsorption conformation of reactant alkyne and corresponding product alkene on encapsulated Pd surface to make alkyne adsorption on Pd surface with larger adsorption energy than that of alkene, thus achieving the high catalytic selectivity. Graphic Abstract: [Figure not available: see fulltext.]
- Wang, Mengyue,Liu, Xuan,Ren, Kui,Zhou, Yiming,Li, Tianhao,Bi, Yunfei,Kang, Haozhe,Xing, Enhui,Chen, Qiang
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- Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
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Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
- Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
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p. 3685 - 3690
(2021/05/31)
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- Phenylacetylene semihydrogenation over a palladium pyrazolate hydrogen-bonded network
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The palladium azolate/carboxylate network (Pd-dmpzc) catalyses the selective hydrogenation of phenylacetylene to styrene in water. Under optimised conditions, at a Pd:NaBH4 ratio of 1:100 at 40 °C, Pd-dmpzc provided much better results than Pd(OAc)2 or PdCl2(CH3CN)2. Analysis of the recovered catalyst revealed the presence of different Pd2+ species and Pd0 NPs which contributed in the catalytic reaction.
- Augustyniak, Adam W.,Trzeciak, Anna M.
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- Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study
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In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N2 adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m2g?1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.
- Ma, Lei,Jiang, Pengbo,Wang, Kaizhi,Lan, Kai,Huang, Xiaokang,Yang, Ming,Gong, Li,Jia, Qi,Mu, Xiao,Xiong, Yucong,Li, Rong
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- Seed-mediated Growth of Alloyed Ag-Pd Shells toward Alkyne Semi-hydrogenation Reactions under Mild Conditions?
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Ag@Ag-Pdx core-shell nanocomposites with various Ag/Pd ratio were deposited on Ag nanoplates using a seed growth method. When physically loaded on C3N4, Ag@Ag-Pd0.077/C3N4 with optimized Ag/Pd ratio could accomplish high catalytic performance for the semi-hydrogenation of phenylacetylene as well as other aliphatic (both terminal and internal alkynes) alkynes and phenylcycloalkynes containing functional groups (such as ester, hydroxyl, ethyl groups) under room temperature and 1 atm H2. The alloying and ensemble effects are used to interpret such catalytic performance.
- Tan, Taixing,Wang, Cheng,Zheng, Yuqin
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p. 3071 - 3078
(2021/09/13)
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- Design, synthesis of novel 4,5-dihydroisoxazole-containing benzamide derivatives as highly potent FtsZ inhibitors capable of killing a variety of MDR Staphylococcus aureus
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Antibiotic resistance among clinically significant bacterial pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) is becoming a prevalent threat to public health, and new antibacterial agents with novel mechanisms of action hence are in an urgent need. As a part of continuing effort to develop antibacterial agents, we rationally designed and synthesized two series of 4,5-dihydroisoxazol-5-yl and 4,5-dihydroisoxazol-3-yl-containing benzamide derivatives that targeted the bacterial cell division protein FtsZ. Evaluation of their activity against a panel of Gram-positive and -negative pathogens revealed that compound A16 possessing the 4,5-dihydroisoxazol-5-yl group showed outstanding antibacterial activity (MIC, ≤0.125–0.5 μg/mL) against various testing strains, including methicillin-resistant, penicillin-resistant and clinical isolated S. aureus strains. Besides, further mouse infection model revealed that A16 could be effective in vivo and non-toxic to Hela cells. Finally, a detailed discussion of structure-activity relationships was conducted, referring to the docking results. It is worth noting that substituting a 4,5-dihydroisoxazole ring for the isoxazole ring not only broadened the antibacterial spectrum but also resulted in a significant increase in antibacterial activity against S. aureus strains. Taken together, these results suggest a promising chemotype for the development of new FtsZ-targeting bactericidal agents.
- Song, Di,Bi, Fangchao,Zhang, Nan,Qin, Yinhui,Liu, Xingbang,Teng, Yuetai,Ma, Shutao
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supporting information
(2020/09/11)
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- Fabrication of Ni3N nanorods anchored on N-doped carbon for selective semi-hydrogenation of alkynes
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Nickel is a highly active catalyst for the semi-hydrogenation of alkynes. However, the low selectivity of the alkene product caused by the over-hydrogenation reaction on Ni has hindered its practical applications. In this work, we report a new nickel nitride (Ni3N)-catalyzed semi-hydrogenation of alkynes to the corresponding alkenes. The Ni3N nanorods were facilely fabricated via a direct pyrolysis of the solid mixture of nickel acetate tetrahydrate and melamine (Mlm). The Ni3N phase in the optimum catalyst (Ni3N/NC-6/5-550) is shown to be effective and stable in the semi-hydrogenation of alkynes, with a high yield and good selectivity for alkenes (Z/E ratios up to >99/1). Both terminal and internal alkynes bearing a broad scope of functional groups are readily converted into alkenes with good chemo- and stereoselectivity. Notably, it was found that the over-hydrogenation can be markedly suppressed even at high conversion of alkyne. Density functional theory (DFT) calculations reveal that the low interaction between the alkene product and the Ni3N might plays a critical role in the selectivity enhancement.
- Shi, Xiaozhen,Wen, Xin,Nie, Shilin,Dong, Jie,Li, Jingde,Shi, Yongqing,Zhang, Huiling,Bai, Guoyi
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- Nitrogen-fixing of ultrasmall Pd-based bimetallic nanoclusters on carbon supports
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Synthesis of supported Pd-based bimetallic catalysts is of great importance in the heterogeneous catalysis field owing to their optimal geometric and electronic effects. Downsizing active metals to ultrasmall nanocluster (2-reduction at 400–500 °C. Through the nitrogen-fixing strategy, we prepare 9 sub-2 nm Pd-based bimetallic nanocluster catalysts by conventional impregnation process. The prepared supported bimetallic Pd-Pb nanocluster catalyst exhibit a high turnover frequency of 1092 h?1 for the semihydrogenation of phenylacetylene under a mild condition (30 °C, 5 bar H2), along with a high selectivity of >93% to styrene, demonstrating the alloying and small-size effects in the bimetallic nanocluster catalysts.
- Chen, Ping,Liang, Hai-Wei,Shen, Shan-Cheng,Wang, Lei,Xu, Shi-Long,Yin, Peng,Zhang, Le-Le
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p. 297 - 304
(2020/07/03)
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- Phosphonium Phenolate Zwitterion vs Phosphonium Ylide: Synthesis, Characterization and Reactivity Study of a Trimethylphosphonium Phenolate Zwitterion
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4-Methoxy-3-(trimethylphosphonio)phenolate was obtained from a regioselective addition of PMe3 to p-quinone monoacetal. This compound undergoes hydrogen isotope exchange with D2O or CD3CN, and is capable of catalyzing H/D exchange of CD3CN with substrates bearing weakly acidic hydrogens. It exhibits similar reactivity to phosphorus ylides for olefinations of aldehydes. A possible tautomerization between the phosphonium phenolate zwitterion and phosphonium ylide is proposed for the first time to rationalize the unique reactivity.
- Xiao, Jing,Li, Qiang,Shen, Ruwei,Shimada, Shigeru,Han, Li-Biao
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supporting information
p. 5715 - 5720
(2019/11/22)
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- PdCx nanocrystals with tunable compositions for alkyne semihydrogenation
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The palladium carbide (PdCx) material has shown great promise as an efficient catalyst for alkyne semihydrogenation. Difficulties in preparing stable PdCx catalysts have been recognized as the main obstacle. Here, we synthesized a highly stable and durable class of PdCx nanocrystals by treating pre-formed Pd nanocrystals with glucose under hydrothermal conditions. The C/Pd atomic ratios in the resultant PdCx nanocrystals can be varied from 0.04 to 0.18, simply by changing the reaction time. The catalytic results for semihydrogenation of 4-ethynyl-1,1′-biphenyl show that PdC0.18 nanocrystals exhibit an activity with a turnover frequency as high as 7896 h-1, ~7.6 and ~38 times higher than that of commercial Pd/C and Lindlar catalysts, respectively, as well as a selectivity of >99%.
- Guo, Ruiyun,Chen, Qiang,Li, Xiang,Liu, Yaming,Wang, Chaoqi,Bi, Wei,Zhao, Caiyang,Guo, Yanjun,Jin, Mingshang
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supporting information
p. 4714 - 4720
(2019/03/07)
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- Ligand-free nickel-catalyzed semihydrogenation of alkynes with sodium borohydride: A highly efficient and selective process for: Cis -alkenes under ambient conditions
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We report a low-cost and efficient catalytic system, involving in situ generated ligand-free Ni NPs, methanol and sodium borohydride, for the semihydrogenation of alkynes under ambient conditions. This catalytic system exhibits remarkably high activity, satisfactory cis-selectivity for internal alkynes, good stability and general applicability.
- Wen, Xin,Shi, Xiaozhen,Qiao, Xianliang,Wu, Zhilei,Bai, Guoyi
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supporting information
p. 5372 - 5375
(2017/07/06)
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- Highly Selective Semihydrogenation of Alkynes to Alkenes by Using an Unsupported Nanoporous Palladium Catalyst: No Leaching of Palladium into the Reaction Mixture
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We report the highly chemoselective and stereoselective semihydrogenation of alkynes to Z-internal and terminal alkenes by using unsupported nanoporous palladium (PdNPore) as a heterogeneous catalyst under mild reaction conditions (room temperature and 1 atm of H2). The semihydrogenation of various terminal/internal and aromatic/aliphatic alkynes afforded the corresponding alkenes in good chemical yields with high selectivities. PdNPore further showed high chemoselectivity toward terminal alkynes in the presence of internal alkynes, which has not yet been achieved using supported palladium nanoparticle catalysts. H-H heterolysis of H2 on the surface of PdNPore was strongly suggested by deuterium labeling experiments. No Pd leached from PdNPore during the reaction, and the catalyst was easily recovered and reused without a loss of activity.
- Lu, Ye,Feng, Xiujuan,Takale, Balaram S.,Yamamoto, Yoshinori,Zhang, Wei,Bao, Ming
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p. 8296 - 8303
(2017/12/08)
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- A Metal-Free Oxidative Dehydrogenative Diels–Alder Reaction for Selective Functionalization of Alkylbenzenes
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Functionalization of C(sp3)?H bonds under metal-free reaction conditions is a great challenge due to poor bond reactivity. A novel metal-free oxidative dehydrogenative Diels–Alder reaction of alkylbenzene derivatives with alkenes through C(sp3)?H bond functionalization is described. The developed oxidative method provides a straightforward approach to biologically relevant 1,4-phenanthraquinone and isoindole derivatives from readily available starting materials. Furthermore, the synthesis of nitrostyrenes from enylbenzene derivatives by selective C(sp3)?H bond functionalization has been demonstrated.
- Manna, Srimanta,Antonchick, Andrey P.
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supporting information
p. 7825 - 7829
(2017/06/06)
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- TRANSITION METAL CATALYSTS FOR C-O HYDROGENOLYSIS AND HYDRODEOXYGENATION
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Phosphoranimide-metal catalysts and their role in C—O bond hydrogenolysis and hydrodeoxygenation (HDO) are disclosed. The catalysts comprise of first row transition metals such as nickel, cobalt and iron. The catalysts have a metal to anionic phosphoranimide ratio of 1:1 and catalyze C—O bond hydrogenolyses of a range of oxygen-containing organic compounds under lower temperature and pressure conditions than those commonly used in industrial hydrodeoxygenation.
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Paragraph 0191
(2014/07/08)
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- ANTIVIRAL DRUGS FOR TREATMENT OF ARENA VIRUS INFECTION
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Compounds, methods and pharmaceutical compositions for treating viral infections, by administering certain compounds in therapeutically effective amounts are disclosed. Methods for preparing the compounds and methods of using the compounds and pharmaceutical compositions thereof are also disclosed. In particular, the treatment and prophylaxis of viral infections such as caused by the Arenavirus family such as Lassa fever, Argentine hemorrhagic fever, Bolivian hemorrhagic fever, and Venezuelan hemorrhagic fever
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Paragraph 0000159
(2013/08/28)
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- Semivolatile and volatile compounds in combustion of polyethylene
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The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
- Font, Rafael,Aracil, Ignacio,Fullana, Andrés,Conesa, Juan A.
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p. 615 - 627
(2007/10/03)
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- Catalytic ring-attachment isomerization and dealkylation of diethylbenzenes over halide clusters of group 5 and group 6 transition metals
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A molybdenum halide cluster, (H3O)2[(Mo 6Cl8)Cl6]·6H2O, possessing an octahedral metal framework was used as a catalyst in a gas flow reactor under 1 atm of hydrogen. On reaction of p-diethylbenzene, dehydrogenation to ethylstyrene proceeded selectively at 300°C. At 400°C, mutual interconversion of o-, m-, and p-diethylbenzenes proceeded selectively. The ethyl group migrated by an intramolecular 1,2-shift mechanism without yielding disproportionation products. Niobium and tungsten chloride clusters with the same metal framework were also active catalysts for the isomerization of p-diethylbenzene. All the reactions resulted in appreciable yields of dealkylation products. The catalytic activity for isomerization can be ascribed to acid sites on the cluster surface, and the catalytic activity for dealkylation, to the metallic nature of the framework metal.
- Kamiguchi, Satoshi,Kondo, Kunihiko,Kodomari, Mitsuo,Chihara, Teiji
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- Reduction of Alkyl Alkyl, Aryl Alkyl and Cyclic Ketones by Catalytic Hydrogen Transfer over Magnesium Oxide
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The reduction of a series of alkyl alkyl, aryl alkyl and cyclic ketones by catalytic hydrogen transfer (CTR) from isopropyl alcohol over magnesium oxide has been investigated.CTR over MgO was found to be an effective and selective route to the corresponding methanols.At temperatures above 523 K parasubstituted phenylmethanols underwent consecutive dehydration leading to the formation of the corresponding styrene derivative with satisfying yields.These processes were studied in a flow system working continuously.A long-time stability of the catalyst activity has been demonstrated.
- Kijenski, Jacek,Glinski, Marek,Czarnecki, Jacek
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p. 1695 - 1698
(2007/10/02)
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- FLASH VACUUM THERMOLYSIS OF DISPIROALKADIENES
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The Flash Vacuum Thermolysis (FVT) of dispirotetradeca -4,13-diene (7a). dispirotrideca-4,12-diene (7b) and dispirodeca-4,9-diene (7e) at 500-750 deg C is reported.The complicated reaction mixture from 7a and 7b (Scheme 3) included at lower temperatures vinylspiroalkadienes 9, ethylidenespiroalkadiene 10b, β-ethylcycloalkabenzenes 11, while at higher temperatures, p-n-alkyl-(5) and p-sec-alkylstyrenes 14 and p-divinylbenzene (15) dominated.Product formation is explained by invoking diradicals 8,6 and 12 as well as the cyclophanes 1 and 13 as intermediates.For 7e, the product mixture was less complicated and consisted of p-ethylstyrene (5e), 15 and, unexpectedly,p-isopropylstyrene (14e) which contains one carbon more than the starting material.The analysis and interpretation of product formation largely confirms previously suggested reaction pathways and furnishes further interesting details.However, new and unexpected features are also encountered, especially in the fragmentations of 1 and 13 which may stimulate future investigations on the thermal behaviour of these relatively simple hydrocarbons.
- Kraakmann, P. A.,Nibbering, E. T. J.,Wolf, W. H. de,Bickelhaupt, F.
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p. 5109 - 5124
(2007/10/02)
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- SCOPE AND LIMITATIONS OF THE FLASH VACUUM THERMOLYSIS APPROACH TO SMALL PARACYCLOPHANES
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Flash vacuum thermolysis (FVT) of 3-methylene-6-spirocyclohexa-1,4-dienes (2) was investigated as a synthetic approach to small paracyclophanes 1 (1a, n=8; 1b, n=7; 1c, n=6).The method was found to be preparatively attractive for 1a (80percent yield), less so for 1b (7percent useful yield), and not at all for 1c which was too unstable to survive the conditions of its formation.Besides 1, p-alkylstyrenes (3) and 2-methylbenzocycloalkenes (4) were obtained; the total recovery of monomeric products was good (60-85percent).The temperature dependence of product formation furnished useful information on the mechanisms of formation and decomposition of 1 under the conditions of FVT.
- Jenneskens, L. W.,Wolf, W. H. De,Bickelhaupt, F.
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p. 1571 - 1574
(2007/10/02)
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- A comparative investigation of 1,4-pentamethylene and 1,4-hexamethylene Dewar benzene. Evidence for the intermediate formation of paracyclophane
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The synthesis of the title compounds 1a and 1b is described.Starting from the corresponding 1,2-dimethylenecycloalkanes 6, the compounds 1 were obtained in four steps, viz. addition of dichlorocarbene, reduction with triphenyltin hydride, treatemnt with potassium tert-butoxide and silver-ion-catalyzed rearrangement.In the last step, the 1,2-isomers 11 of 1 were also formed, and their thermal rearrangement to the benzocycloalkenes 4 is briefly described.Compound 1b rearranged to its aromatic isomer (6)paracyclophane (2b) both thermally (60 deg C in solution, 100-460 deg C flow pyrolysis) and under silver-ion catalysis at room temperature; in this latter reaction the initially formed 2b was gradually further isomerized to 4b.At higher temperatures, 2b rearranged to the spirotrienes 3b and finally fragmented to give p-ethylstyrene (17).From 1a, the spirotriene 3a and benzocycloheptene (4a) were obtained by thermolysis and by silver-ion catalysis, respectively.The mechanism of these reactions is discussed and it is concluded that (5)paracyclophane (2a) is a transient intermediate in th reaction of 1a.
- Straten, J. W. van,Turkenburg, L. A. M.,Wolf, W. H. de,Bickelhaupt, F.
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