22495-71-2Relevant articles and documents
Trace mild acid-catalysedZ→Eisomerization of norbornene-fused stilbene derivatives: intelligent chiral molecular photoswitches with controllable self-recovery
Hao, Taotao,Yang, Yongsheng,Liang, Wenting,Fan, Chunying,Wang, Xin,Wu, Wanhua,Chen, Xiaochuan,Fu, Haiyan,Chen, Hua,Yang, Cheng
, p. 2614 - 2622 (2021/03/01)
Stilbene derivatives have long been known to undergo “acid-catalyzed”Z→Eisomerization, where a strong mineral acid at high concentration is practically necessary. Such severe reaction conditions often cause undesired by-reactions and limit their potential application. Herein, we present a trace mild acid-catalyzedZ→Eisomerization found with stilbene derivatives fused with a norbornene moiety. By-reactions, such as the migration of the C-C double bond and electrophilic addition reactions, were completely inhibited because of the ring strain caused by the fused norbornene component. Direct photolysis of theEisomers at selected wavelengths led to theE→Zphotoisomerization of these stilbene derivatives and thus constituted a unique class of molecular switches orthogonally controllable by light and acid. The catalytic amount of acid could be readily removed, and theZ→Eisomerization could be controlled by turning on/off the irradiation of a photoacid, which allowed repeated isomerization in a non-invasive manner. Moreover, theZisomer produced by photoisomerization could spontaneously self-recover to theEisomer in the presence of a catalytic amount of acid. The kinetics ofZ→Eisomerization were adjustable by manipulating catalytic factors and, therefore, unprecedented molecular photoswitches with adjustable self-recovery were realized.
Polymerization of ethene with zirconocene catalysts: An experimental and quantum chemical study of the influence of para-substituent in benzyl in bis{η5-(1-benzyl)indenyl}zirconium dichlorides
Aitola, Erkki,Surakka, Marina,Repo, Timo,Linnolahti, Mikko,Lappalainen, Kristian,Kervinen, Kaisa,Klinga, Martti,Pakkanen, Tapani,Leskel?, Markku
, p. 773 - 783 (2007/10/03)
The meso- and rac-like isomers of bis{η5-(1-benzyl)indenyl} zirconium dichloride (5), bis{η5-(1-para-methoxybenzyl)indenyl} zirconium dichloride (6), bis{η5-(1-para-fluoro-benzyl)indenyl} zirconium dichloride (7) and bis{η5-(1-phenylethyl)indenyl} zirconium dichloride (8) were synthesized and isolated. Solid-state structures of meso- and rac-like 5 were determined by X-ray structure analysis. Polymerization properties of the methylaluminoxane (MAO) activated diastereomers of complexes 5-8 were studied in ethene polymerizations under different monomer concentrations. The rac-like isomer of 1-phenylethyl-substituted 8/MAO showed significantly higher activity than the 1-benzyl substituted analogs 5-7/MAO. In addition, rac-8/MAO behaves like a single center catalyst producing polyethene with narrow molar mass distribution (1.8-1.9), while diastereomers of 5-7/MAO produce polymers with molar mass distributions varying from 2.7 up to 10.3. The rac and meso-like isomers of 5-7/MAO have different response on the monomer concentration. Quantum chemical calculations suggest a strong interaction between the benzyl substituent and the electron deficient zirconium center. The phenyl metal coordination energies depend on the electronic properties of the para-substituent. In 8/MAO, due to the ethyl spacer, the coordination does not have a significant role and therefore much higher activity and single center polymerization behavior is observed.
Photochemistry of 2-Vinylstilbene, 1,2-Distyrylbenzene, and 2,2'-Distyrylbiphenyl Absorbed on Silica Gel. Influence of Ground-State Conformers on Formation of Photoproducts
Tol, Arie J. W.,Laarhoven, Wim H.
, p. 1663 - 1668 (2007/10/02)
Irradiation of 2-vinylstilbene (1) absorbed on silica gel gives rise to several products.In addition to exo- and endo-5-phenylbenzobicyclohex-2-enes (2 and 3) (the sole products formed in solution) derivatives of naphthalene and of indene are forme
