89044-50-8Relevant academic research and scientific papers
Crystal structure and propene polymerization characteristics of bridged zirconocene catalysts
Kaminsky, W.,Rabe, O.,Schauwienold, A. -M.,Schupfner, G. U.,Hanss, J.,Kopf, J.
, p. 181 - 194 (1995)
The synthesis, crystal structure and propene polymerization behaviour of four bridged zirconocene dichlorides is presented.All catalysts are capable of isotactic propene polymerization.Methyl substitutions at the 2-, 4- and 7-positions of the bridged bis(indenyl)zirconocene dichlorides were introduced.The methyl substituent in the 7-position of the indenyl ring induces a significant steric interaction with the bridging group.On comparison of the 2,4,7-methyl substituted catalysts with their unsubstituted counterparts, only the ethylidene bridged catalyst rac-1,2-ethylidene- bis(2,4,7-trimethyl-1-indenyl)zirconium dichloride (4) is forced into the optimum geometry for isotactic propene polymerization.Owing to the steric bulk at the bridge catalyst 4 is very rigid with respect to the movement of the indenyl rings and the metal centre thus produces highly isotatic polypropene even up to high polymerization temperatures.Molecular mechanics calculations and temperature-dependent NMR measurements demonstrate that catalyst 4 is not able to equilibrate between the λ and δ conformational state as the corresponding rac-1,2-ethylidene-bis(-1-indenyl)zirconium dichloride (3) catalyst does.In the case of the catalyst isopropyliden(3-tert-butyl)cyclopentadienyl-9-fluorenyl)zirconium dichloride (6) the substitution in the 3-position changes the symmetry from Cs to C1.This catalyst produces isoactic polypropylene but with a decreased polymerization activity.Keywords: Zirconocene; Homogeneous Ziegler-Natta catalysis; Propene polymerization; Molecular mechanics calculations
A redesign of light-driven rotary molecular motors
Pollard, Michael M.,Meetsma, Auke,Feringa, Ben L.
, p. 507 - 512 (2008)
Structural modification of unidirectional light-driven rotary molecular motors in which the naphthalene moieties are exchanged for substituted phenyl moieties are reported. This redesign provides an additional tool to control the speed of the motors, and should enable the design and synthesis of more complex systems. The Royal Society of Chemistry 2008.
Novel crown-ether compound and preparation method thereof
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Paragraph 0047; 0050-0052, (2019/02/04)
The invention relates to a crown-ether compound. The crown-ether compound is a compound as shown in a formula I or an isomer of the compound. The crown-ether compound provided by the invention can form a complex with ammonium salt, and after the lighting
Fluorine-Substituted Molecular Motors with a Quaternary Stereogenic Center
?tacko, Peter,Kistemaker, Jos C. M.,Feringa, Ben L.
, p. 6643 - 6653 (2017/05/15)
A series of unprecedented second generation molecular motors featuring a quaternary stereogenic center substituted with a fluorine atom has been synthesized. It is demonstrated that a seemingly benign replacement of the stereogenic hydrogen for a fluorine atom, regarded as a common substituent in pharmacology, resulted in a dramatic change in the energetic profile of thermal helix inversion. The barrier for the thermal helix inversion was found to increase considerably (by 20–30 kJ mol?1), presumably due to destabilization of the transition state by increased steric hindrance when the fluorine atom is forced to pass over the lower half of the motor. This results in the activation barrier for the thermal helix inversion to be higher than the barrier for backward thermal E–Z isomerization, impairing the motor function. A fluorine-substituted motor capable of performing unidirectional rotation is successfully prepared when these limitations are considered in the design phase.
A bridge linking and its application of metal complexes
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, (2017/02/23)
The invention discloses a bridged metallocene complex, which is characterized by having a structural formula shown as the following A1, A2, A3 or A4. The invention also discloses a preparation method of ethylene propylene rubber. The ethylene propylene ru
A method of preparation of ethylene-propylene-diene rubber
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, (2017/03/23)
The invention discloses a bridged metallocene complex, which is characterized by having a structural formula shown as the following A1, A2, A3 or A4. The invention also discloses a preparation method of ethylene propylene rubber. The ethylene propylene ru
Ligand compound, catalyst system for olefin oligomerization, and method for olefin oligomerization using the same
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Paragraph 0090-0095, (2017/01/02)
This disclosure relates to a ligand compound, a catalyst system for olefin oligomerization, and a method for olefin oligomerization using the same. The catalyst system for olefin oligomerization according to the present invention has excellent catalytic activity, and yet, exhibits high selectivity to 1-hexene and 1-octene, thus enabling efficient preparation of alpha-olefin.
LIGAND COMPOUND, CATALYST SYSTEM FOR OLEFIN OLIGOMERIZATION, AND METHOD FOR OLEFIN OLIGOMERIZATION USING THE SAME (As Amended)
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Paragraph 0075, (2016/11/09)
This disclosure relates to a ligand compound, a catalyst system for olefin oligomerization, and a method for olefin oligomerization using the same. The catalyst system for olefin oligomerization according to the present invention has excellent catalytic activity, and yet, exhibits high selectivity to 1-hexene and 1-octene, thus enabling efficient preparation of alpha-olefin.
Preparation of trifluoromethylated dihydrocoumarins, indanones, and arylpropanoic acids by tandem superacidic activation of 2-(Trifluoromethyl) acrylic acid with arenes
Prakash, G. K. Surya,Paknia, Farzaneh,Vaghoo, Habiba,Rasul, Golam,Mathew, Thomas,Olah, George A.
supporting information; experimental part, p. 2219 - 2226 (2010/06/15)
Chemical Reaction Reprentation Indanones and coumarins are important intermediates for the convenient synthesis of many pharmaceutical and biologically active compounds. Fluoroorganics play a vital role in the design of very effective therapeutics due to significant enhancenment in their lipophilicity, bioavailability, and fast uptake by the presence of fluorine in these molecules. Herein, we report an efficient one-pot synthesis of trifluoromethylated arylpropanoic acids, indanones, and dihydrocoumarins using Friedel-Crafts alkylation or tandem Friedel-Crafts alkylation-cycloacylation of arenes/phenols with 2-(trifluoromethyl)acrylic acid under superacidic conditions using trifluoromethanesulfonic acid. The results have been rationalized by the structure energy calculations of the involved reaction intermediates using ab initio theoretical methods.
Process for the preparation of amorphous polymers of propylene
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, (2008/06/13)
It is possible to prepare substantially amorphous polymers of propylene endowed with high molecular weights, operating at temperatures of industrial interest, by carrying out the polymerization reaction of propylene in the presence of metallocene catalysts comprising particular bis-indenyl or bis-4,5,6,7-tetrahydroindenyl compounds substituted in the 2-position on the indenyl or tetrahydroindenyl groups.
