5400-80-6Relevant articles and documents
Dissymmetric ansa zirconocene complexes with di- and trisubstituted indenyl ligands as catalysts for homogeneous ethylene homo- and ethylene/1-hexene copolymerization reactions
Rimkus, Andrea M.,Alt, Helmut G.
, p. 72 - 82 (2017/02/18)
Different routes for the synthesis of 1,2- and 1,2,3-substituted indene derivatives are described. Representative substituents are: Me, Ph, PhCH2, PhCH2CH2, PhCH2CH2CH2, CH2CH?=?CH2. Subsequent deprotonation of these substituted indenes and reaction with indenyl zirconium trichloride gave the corresponding dissymmetric bis(indenyl) zirconium complexes. After activation with methylaluminoxane (MAO) these complexes show high activities both in ethylene homopolymerisation and ethylene/1-hexene copolymerisation. The rate of comonomer incorporation can reach 33.3% (15/MAO). The copolymers exhibit lower melting points than the homopolymers and their crystallinities α are lower compared with the homopolymers.
Unbridged 1- and 2-substituted bis(silylindenyl) zirconium(IV) and hafnium(IV) dichloride complexes as catalyst precursors for ethylene polymerization
Abdelbagi, Mohamed E.M.,Alt, Helmut G.
, p. 284 - 295 (2017/09/20)
Twelve unbridged metallocene dichloride complexes of the types [1-(4-XC6H4SiMe2)-η5-Ind]2MCl2 and [2-(4-XC6H4SiMe2)-η5-Ind]2MCl2 (X = Me, MeO, F; M = Zr, Hf) with differently 1- and 2-substituted indenyl ligands have been synthesized, characterized and applied for catalytic ethylene polymerization. After activation with methylaluminoxane (MAO), all complexes are catalysts for ethylene polymerization. However, in nearly all cases, the species with the silyl substituent in the 1-position show much higher activities than those with the same substituent in 2-position of the indenyl moiety. For instance, the MAO activated complex bis(η5-1-(dimethyl-4-tolylsilyl)idenyl) zirconium(IV) dichloride (3), displayed an almost five times higher activity (3980 kg PE/mol cat.h) than the isomeric bis(η5-2-(dimethyl-4-tolylsilyl)indenyl) zirconium(IV) dichloride (19)/MAO catalyst (870 kg PE/mol cat.h). The same trend was observed for the para-fluorophenyl silyl indenyl complexes 23 and 17. This behavior may be explained in a way that the same silyl substituent in position 2 can exert more steric hindrance around the metal center compared to the 1-substituted analogues. The GPC characterization of the produced polyethylenes showed that some of the resins have a bimodal molecular weight distribution indicating at least two different active sites that are involved in the polymerization process.
METALLOCENE COMPOUND AND METHOD OF PREPARING THE SAME (As Amended)
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Paragraph 0127; 0136, (2016/08/07)
Provided are a metallocene compound having a novel structure capable of preparing a polyolefin having a broad molecular weight distribution and a high molecular weight, and a method of preparing the same. The metallocene compound according to the present invention includes a non-crosslinked catalyst structure, and implements copolymerizability in an ansa-type catalyst level, thereby preparing a polyolefin having a high molecular weight of 300,0000 or more.
The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
supporting information, p. 14740 - 14749 (2016/11/18)
The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
On the bromination of aromatics, alkenes and alkynes using alkylammonium bromide: Towards the mimic of bromoperoxidases reactivity
Mendoza, Fabian,Ruíz-Guerrero, Rosario,Hernández-Fuentes, Carlos,Molina, Paulina,Norzagaray-Campos, Mariano,Reguera, Edilso
supporting information, p. 5644 - 5648 (2016/11/28)
This article describes an efficient method of bromination of organic substrates including aromatics, alkenes and alkynes with NH4VO3as a catalyst and H2O2as an oxidant agent using a non-toxic and easy-to-handle source of bromine, tetrabutylammonium bromide. The process was developed under mild reaction conditions and is an innovation from reported methods in aspects such as: i) short reaction times, ii) the ability to work at room temperature, iii) regioselectivity and good yields.
NOVEL CYCLOALKENE DERIVATIVES AND ORGANIC ELECTRONIC DEVICES USING THE SAME
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Page/Page column 20-21, (2011/12/12)
The present invention relates to a novel cycloalkene derivative, and an organic electronic device using the same. The cycloalkene derivative according to the exemplary embodiment of the present invention may act as a hole injection, a hole transport, an electron injection, an electron transport, or a light emitting material in an organic light emitting diode and an organic electronic device, and in particular, may be used alone as a light emitting host or a dopant.
Facile one-pot synthesis of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent
Patil, Rajendra D.,Joshi, Girdhar,Adimurthy, Subbarayappa,Ranu, Brindaban C.
experimental part, p. 2529 - 2532 (2009/09/06)
A new method for the preparation of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent has been developed. Several α-bromoketones were successfully prepared from a variety of olefins by this method. This procedure is an alternative to conventional molecular bromine.
Microbiological transformations 32: Use of epoxide hydrolase mediated biohydrolysis as a way to enantiopure epoxides and vicinal diols: Application to substituted styrene oxide derivatives
Pedragosa-Moreau,Archelas,Furstoss
, p. 4593 - 4606 (2007/10/03)
The biohydrolyses of various substituted styrene oxide derivatives using the fungi Aspergillus niger or Beauveria sulferescens are described. The results obtained show that this methodology allows the preparation of enantiomerically enriched epoxides and diols via enantioselective and regioselective hydration. The comparative study of the results obtained suggests that these hydrolyses operate following different mechanisms and a model of the corresponding active sites is proposed.
Synthesis of brominated compounds. A convenient molybdenum-catalyzed procedure inspired by the mode of action of haloperoxidases
Conte, Valeria,Di Furia, Fulvio,Moro, Stefano
, p. 8609 - 8612 (2007/10/03)
A two-phase (CHCl3/H2O) procedure for the synthesis of halogenated compounds has recently been developed. Such procedure mimics the mode of action of the enzymes haloperoxidases which contain vanadium in their active center. We have investigated the possibility to substitute vanadium with molybdenum. The molybdenum-based reactions show some advantages over the vanadium-based ones. In fact reaction times are shorter and overall yields are larger, under similar experimental conditions, both in the reaction with double bonds as well as with aromatic rings. Moreover, with double bonds, the molybdenum catalyzed process preferentially yields bromohydrins which are valuable synthetic intermediates. On the other hand, the molybdenum-catalyzed reactions show peculiar mechanistic features which deserve further investigation.
Efficient Intramolecular General Acid Catalysis of Enol Ether Hydrolysis. Hydrogen-bonding Stabilisation of the Transition State for Proton Transfer to Carbon
Kirby, Anthony J.,Williams, Nicholas H.
, p. 643 - 648 (2007/10/02)
The intrinsically low efficiency of intramolecular general acid-base catalysis is enhanced when the proton transfer generates a strong intramolecular hydrogen bond.This principle is shown to apply to proton transfer to carbon: the carboxy groups of methyl vinyl ethers 3E and 3Z derived from 2-carboxyphenylacetaldehyde act as general acids to catalyse the hydrolysis of the neighbouring enol ether groups with effective molarities (EM) of about 300 and 2000 M, respectively.The solvent deuterium isotope effects confirm that the usual mechanism for enol ether hydrolysis is operative.In this system the oxocarbocation intermediate is trapped by the neighbouring carboxylate group to give the acylal 6, rather than the formal product of hydrolysis.
