4249-10-9Relevant articles and documents
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 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.
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).
