4249-10-9Relevant academic research and scientific papers
Preparation process of tetramethyl cyclopentadiene
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Paragraph 0053; 0056; 0057; 0060; 0061; 0064; 0065; 0068, (2021/05/01)
The invention provides a preparation process of tetramethyl cyclopentadiene, which comprises the following steps: A) uniformly mixing tetramethyl cyclopentenone, alcohol and a catalyst to obtain a mixed solution; B) dropwise adding a NaBH4 solution into the mixed solution, and carrying out a reduction reaction to obtain a reaction mixed solution, wherein the NaBH4 solution is prepared from NaBH4, alcohol, NaOH and water; C) adding water into the reaction mixed solution, and extracting organic matters in the reaction mixed solution by using an extracting agent; and D) adding sulfuric acid into the organic matter extracted in the step C), and dehydrating to obtain tetramethyl cyclopentadiene. According to the reaction system disclosed by the invention, tetramethyl cyclopentenone is reduced into tetramethyl cyclopentene alcohol by sodium borohydride under a mild condition by adjusting the conditions such as the catalyst, the solvent, the reaction temperature and the reaction time, and tetramethyl cyclopentadiene can be prepared after dehydration.
Preparation method 1, 2, 3, 4 - tetramethyl -1 and 3 - cyclopentadiene
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Paragraph 0051; 0055-0073; 0076-0079, (2021/09/29)
The invention relates to the technical field of chemical synthesis, in particular to a preparation method of 1, 2, 3, 4 - tetramethyl -1 and 3 - cyclopentadiene, which comprises A) carrying out a metal supported catalyst under the condition of hydrogen. 2, 3, 4, 5 -tetramethyl -2 - cyclopentene ketone and a solvent are subjected to hydrogenation reaction to obtain 2, 3, 4 and 5 -tetramethyl -2 - cyclopentanol. A metal supported catalyst comprises a solid support and a metal supported on the solid support. The metal element is selected from one or both of the VIII th main group elements. B) Under the action of a strong acid resin catalyst, 2, 3, 4 and 5 - tetramethyl -2 - cyclopentanol are subjected to dehydration reaction to obtain 1, 2, 3, 4 - tetramethyl -1 and 3 - cyclopentadiene. After the hydrogenation reaction is finished, only simple filtration removal is needed, solid waste liquid is not generated, acid is not needed for neutralization, waste acid water which is difficult to handle is not generated, and the product yield is high.
Preparation method of 1, 2, 3, 4-tetramethyl-1, 3-cyclopentadiene
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Paragraph 0037; 0046-0080, (2020/06/30)
The invention belongs to the technical field of chemical synthesis, and particularly relates to a preparation method of 1, 2, 3, 4-tetramethyl-1, 3-cyclopentadiene. The preparation method provided bythe invention comprises the following step: in the presence of a solid acid catalyst, carrying out dehydration reaction on 2, 3, 4, 5-tetramethyl-2-cyclopentenol in a solvent to obtain 1, 2, 3, 4-tetramethyl-1, 3-cyclopentadiene, wherein the solid acid catalyst comprises a strongly acidic resin catalyst and/or a solid superacid catalyst. According to the preparation method, 2, 3, 4, 5-tetramethyl-2-cyclopentenol is used as a raw material and is subjected to dehydration reaction under the action of a specific solid acid catalyst to obtain a target product (1, 2, 3, 4-tetramethyl-1, 3-cyclopentadiene). The preparation method provided by the invention can effectively inhibit the generation of by-products, the product is high in selectivity and easy to separate, no solid waste or waste acid water is generated, and good economic benefits and environmental benefits are achieved.
Tuning the photochemical properties of the fulvalene-tetracarbonyl-diruthenium system
Lennartson, Anders,Lundin, Angelica,B?rjesson, Karl,Gray, Victor,Moth-Poulsen, Kasper
supporting information, p. 8740 - 8744 (2016/06/09)
In a Molecular Solar-Thermal Energy Storage (MOST) system, solar energy is converted to chemical energy using a compound that undergoes reversible endothermic photoisomerization. The high-energy photoisomer can later be converted back to the parent compound and the excess energy is released as heat. One of the most studied MOST systems is based on fulvalene-tetracarbonyl-diruthenium, and this paper demonstrates, for the first time, the possibility to tune the photochemical properties of this system by positive steric hindrance working on the fulvalene unit.
Ytterbium(III) Complexes Coordinated by Dianionic 1,4-Diazabutadiene Ligands
Shestakov, Boris G.,Mahrova, Tatyana V.,Larionova, Joulia,Long, Jêrome,Cherkasov, Anton V.,Fukin, Georgy K.,Lyssenko, Konstantin A.,Scherer, Wolfgang,Hauf, Christoph,Magdesieva, Tatiana V.,Levitskiy, Oleg A.,Trifonov, Alexander A.
, p. 1177 - 1185 (2015/04/27)
A series of new Yb(III) complexes XYb(DAD)2-(L) (X = C5Me5, C5Me4H, N(SiMe3)2, tBuO; DAD = 2,6-R″2C6H3N=C(R′)-C(R′)=NC6H3R″2-2,6, R′ = H, Me, R″ = Me, iPr; L = thf, dme) coordinated by redox-active diazabutadiene ligands in dianionic form were synthesized and characterized. The half-sandwich complexes Cp#Yb(DAD)2-(THF) (Cp# = C5Me5, C5Me4H) were synthesized by the reactions of the ytterbocenes Cp#2Yb(THF)2 with the corresponding DADs in a 1:1 molar ratio. These reactions are accompanied by oxidation of the Yb(II) to Yb(III), cleavage of one Cp#-Yb bond, oxidation of cyclopentadienyl anion, and reduction of the diazabutadiene to dianionic form. It was found that the substituents by the DAD nitrogens (2,6-iPr2C6H3 vs 2,6-Me2C6H3) and imino carbons (H vs Me) do not affect the reaction outcome and afford Cp#Yb(DAD)2-(thf). The amido and alkoxo derivatives XYb(DAD)2-(dme) (X = N(SiMe3)2, tBuO) were obtained by the salt metathesis reactions of the in situ generated species [XYbCl2(thf)n] and Na2(thf)n[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6]. If the reaction was carried out in the presence of Li ions, it afforded an ate-complex {Li(thf)3}{Yb[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6]2-[N(SiMe3)2](μ-Cl)}. The X-ray studies of complexes XYbIII(DAD)2-(L) revealed that they feature the 2σ:η2-type of coordination of dianionic DAD ligands. Introduction of Me-substituents by the imino carbons of DADs leads to some elongation of Yb-Cp# bonds compared to the NCHCHN-analogues. The Yb-CNCCN bonds and the dihedral YbNN-NCCN angles were found to be the most sensitive to replacing H by Me. Unlike the formerly reported complex Cp?Yb[2,6-iPr2C6H3NCHCHNC6H3iPr2-2,6]2-(thf), the variable-temperature magnetic measurements (1.8-300 K) of complexes 3-5 and 7-9 did not reveal thermally induced redox isomeric transformations for these compounds. However, for complex (C5Me4H)Yb[2,6-iPr2C6H3NC(Me)C(Me)NC6H3iPr2-2,6](thf) at 9 K, the structural phase transition accompanied by changes of the coordination behavior of the DAD ligand was detected, which might hint for an onset of a temperature-induced redox isomerism. These results clearly indicate high sensitivity of redox isomeric transformations of XYbIII(DAD)2-L to the smallest changes of the structural and electronic properties of the DAD ligands. (Chemical Equation Presented).
Synthesis and structures of ansa-titanocene complexes with diatomic bridging units for overall water splitting
Kessler, Monty,Hansen, Sven,Godemann, Christian,Spannenberg, Anke,Beweries, Torsten
supporting information, p. 6350 - 6357 (2013/07/05)
The synthesis of a series of ansa-titanocene dichlorides [Cp' 2TiCl2] (Cp′=bridged η5- tetramethylcyclopentadienyl) and the corresponding titanocene bis(trimethylsilyl)acetylene complexes [Cp′2Ti(η 2-Me3SiC2SiMe3)] is described. The ethanediyl-bridged complexes [C2H4(C5Me 4)2TiCl2] (2-Cl2) and [C 2H4(C5Me4)2Ti(η 2-Me3SiC2SiMe3)] (2-btmsa; btmsa=η2-Me3SiC2SiMe3) can be obtained from the hitherto unknown calcocenophane complex [C2H 4(C5Me4)2Ca(THF)2] (1). Furthermore, a heterodiatomic bridging unit containing both, a dimethylsilyl and a methylene group was introduced to yield the ansa-titanocene dichloride [Me2SiCH2(C5Me4) 2TiCl2] (3-Cl2) and the bis(trimethylsilyl) acetylene complex [Me2SiCH2(C5Me 4)2Ti(η2-Me3SiC 2SiMe3)] (3-btmsa). Besides, tetramethyldisilyl- and dimethylsilyl-bridged metallocene complexes (structural motif 4 and 5, respectively) were prepared. All ansa-titanocene alkyne complexes were reacted with stoichiometric amounts of water; the hydrolysis products were isolated as model complexes for the investigation of the elemental steps of overall water splitting. Compounds 1, 2-btmsa, 2-(OH)2, 3-Cl2, 3-btmsa, 4-(OH)2, 3-alkenyl and 5-alkenyl were characterised by X-ray diffraction analysis. Copyright
1,4-HYDROGENATION OF DIENES WITH RU COMPLEXES
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Page/Page column 13, (2008/12/04)
The present invention relates to the use of Ru complexes, having a cyclopentadienyl derivatives and a diene as ligands, together with some acidic additives for improving the selectivity in the 1,4-hydrogenation of conjugated dienes into the corresponding "cis "-alkene as major product, i.e. wherein the two substituents in position 2,3 of said diene are in a cis configuration in the corresponding alkene.
Synthesis and electrochemical properties of slipped-cofacial porphyrin dimers of ferrocene-functionalized Zn-imidazolyl-porphyrins as potential terminal electron donors in photosynthetic models
Kalita, Dipak,Morisue, Mitsuhiko,Kobuke, Yoshiaki
, p. 77 - 92 (2007/10/03)
A systematic series of ferrocene-functionalized Zn-imidazolyl-porphyrins were synthesized to assemble into the slipped-cofacial porphyrin dimers through imidazolyl-to-zinc complementary coordination as artificial photosynthetic models. Direct substitution at the meso position of the porphyrin ring with ferrocence and octamethylferrocene leads to the characteristic electronic structures, while the ferrocene substituents through phenylene-ethenylene and phenylene-ethylene spacers mitigate the electronic communications. Bathochromic shift of Q band, fluorescence quenching, and redox potentials of porphyrin ring are rationalized by the degree of electron-donating ability of the terminal ferrocenes. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
Synthesis of Tetraalkylcyclopentadienes
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Page column 4, (2008/06/13)
A method for synthesizing tetramethylcyclopentadiene from 2,3-dibromobutane is described. A 2-bromo-2-butene Grignard is reacted with an ethyl formate to produce a 3,5-dimethyl-2,5-heptadiene-4-ol magnesium bromide which is then quenched with acetic acid to produce 3,5-dimethyl-2,5-hepadiene-4-ol.
Chiral metallocenes: The synthesis and X-ray crystal structures of TiCl2(η5:η5-C5Me 4SiMe2C5H3R*) (R* = menthyl or neomenthyl) and related compounds
Beagley,Davies,Adams,White
, p. 731 - 741 (2007/10/03)
The syntheses of the chiral ansa-metallocene complexes TiCl2(η5:η5-C5 Me4SiMe2C5H3R*) (R* = menthyl (4a) or neomenthyl (4b)) are reported; initially 4a was obtained as a 3:1 mixture of (R:S) diastereoisomers, which differ only in which face of the asymmetrically substituted cyclopentadienyl ring is bonded to the titanium (chiral descriptor shown). The major diastereomer 4aR was crystallized out optically pure from the initial reaction mixture, whereas the 4aS diastereoisomer was isolated after isomerizing a racemic mixture of 4a to a 1:3 mixture of (R:S) diastereoisomers using UV irradiation. The corresponding neomenthyl complex 4b was obtained as a 1.3:1 mixture of diastereoisomers that could not be separated. The optically pure 4aR was converted stereoselectively into the corresponding (R)-TiMe2(η5:η5-C5Me 4SiMe2C5H3R*) (R* = menthyl). Syntheses of the related indenyl ligand system C5Me4SiMe2C9H7 (3) is reported but complexation to titanium proved to be problematic although ZrCl2(η5:η5-C5Me 4SiMe2C9H6) (6) was isolated. The crystal structures of both 4aR and 4aS are reported and compared. Crystals of 4aR are orthorhombic, a = 27.857(11), b = 9.985(5), and c = 9.596(4) A, Z = 4, space group P212121 (D24, No. 19), and those of 4aS are monoclinic, a = 8.5810(10), b = 38.679(4), and c = 8.5842(10) A β = 113.001(2)°, Z = 4, space group P21 (C22, No. 4). The structures were solved by the Patterson method and 4aR was refined by blocked-cascade least-squares procedures to R = 0.0628 (Rω = 0.0503) for 902 reflections with |F|/σ(|F|) ≥ 3.0, whereas 4aS was refined by full-matrix least-squares procedures to R = 0.0646 (wR2 = 0.1829) for 5734 reflections with |F|/σ(|F|) ≥ 4.0. Both diastereomers of 4a catalyze hydrosilylation of ketones, but as expected from a comparison of the two crystal structures, the 4aR isomer is the more stereoselective catalyst, i.e., hydrosilylation of acetophenone followed by hydrolysis gives 82% enantiomeric excess (ee) of (S)-PhCH(Me)OH with 4aR whereas only 16% ee of (R)-PhCH(Me)OH with 4aS.
