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Styrene Derivatives (styrene + derivative)
Selected AbstractsSynthesis of Functionalized 1-Substituted Alkenylsilanols and Establishment of Conditions for Their Palladium-Catalyzed Cross-Coupling Reactions To Afford 1-Substituted Styrene DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2004Sunil K. Ghosh Abstract An efficient method for the quantitative conversion of 1-substituted alkenyl(phenyl)silanes into the corresponding alkenylsilanols has been developed and used in their palladium(0)-catalyzed, tetrabutylammonium fluoride-promoted cross-coupling reaction with aryl iodides. Copper(I) chloride modulated the reactivity of TBAF in such a way that it virtually eliminated the protiodesilylation of alkenylsilanols, thus favoring the formation of ipso -coupled products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A Convenient Method for the Synthesis of 2-Arylaziridines from Styrene Derivatives via 2-Arylethenyl(diphenyl)sulfonium Salts.CHEMINFORM, Issue 31 2003Jun-ichi Matsuo Abstract For Abstract see ChemInform Abstract in Full Text. [source] On the Origin of the Facial Selectivity of the Sharpless Asymmetric Dihydroxylation of Styrene Derivatives.CHEMINFORM, Issue 26 2003Nicolas Moitessier Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Regioselective Synthesis of Substituted 3,4-Dihydro-2H-thiines from ,,,-Unsaturated Oxathiolanes and Styrene Derivatives.CHEMINFORM, Issue 11 2002Sebastien Kerverdo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: New C2 -Symmetrical 1,2-Diphosphanes for the Efficient Rhodium-Catalyzed Asymmetric Hydroboration of Styrene Derivatives.CHEMINFORM, Issue 30 2001Stephane Demay Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Reactions of a Cyclotrisilane with Styrene Derivatives and Diarylacetylenes , Evidence for Nucleophilic Silylenes.CHEMINFORM, Issue 19 2001Johannes Belzner Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis of 1-Aryl-1H-indole Derivatives by Iodine-Mediated Cyclization of 2-(Arylamino)styrene Derivatives.CHEMINFORM, Issue 7 2007Kazuhiro Kobayashi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Asymmetric Total Synthesis of Fredericamycin A: An Intramolecular Cycloaddition PathwayCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2005Shuji Akai Dr. Abstract The asymmetric total synthesis of the potent antitumor antibiotic fredericamycin A ((S)- 1) was achieved by the intramolecular [4+2] cycloaddition of the silylene-protected styrene derivative (S)- 7 followed by the aromatic Pummerer-type reaction of the sulfoxide (S)- 5. Although we had already succeeded in the total synthesis of racemic 1 by the same approach, synthesis of its asymmetric version was more complicated than we had expected due to the difficulties involved in constructing the quaternary carbon center and the tendency of this center to undergo facile racemization. Racemization of this center during the installation of the acetylene moiety on the dione (R)- 8 was the most serious aspect. Systematic studies of its DE-ring analogue (R)- 25 revealed that racemization of the quaternary carbon center proceeded by a retro-aldol,aldol reaction of the initial adduct, (1R)- 39,a -Li, and that the degree of racemization was dependent on the reaction temperature. The racemization process could be completely depressed by keeping the reaction temperature at ,78,°C. The construction of the stereogenic quaternary carbon center was achieved by the lipase-catalyzed desymmetrization of the prochiral 1,3-diol 9,a bearing the DEF-ring moiety. These studies enabled us to attain the asymmetric total synthesis of (S)- 1 while completely retaining the chiral integrity created by the enzymatic reactions. [source] Efficient Platinum(II) Catalyzed Hydroformylation Reaction in Water: Unusual Product Distribution in Micellar MediaADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Marina Gottardo Abstract The hydroformylation of a variety of terminal and internal alkenes is efficiently performed by cationic platinum triflate complexes of the type [P2Pt(H2O)2](OTf)2 under mild conditions in an aqueous micellar medium. The use of surfactants is essential to ensure dissolution of the catalyst and substrate in water with catalysts being positioned on the anionic surface of the micelles. Aldehydes are obtained with linear to branched ratios up to >99:1. With styrene derivatives also the corresponding benzaldehydes are formed. The catalyst can be separated by extraction of the organic products with hexane and recycled for at least four times with only a modest loss of activity and no effect on selectivity. [source] Iron-Catalysed Regio- and Stereoselective Head-to-Tail Dimerisation of StyrenesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Abstract Cationic iron salts and complexes catalyse the head-to-tail dimerisation of styrene derivatives to form the corresponding dimers with good to excellent yields and stereoselectivities. In particular, the use of a phosphine-iron(III) complex allows the recovery and reuse of the catalyst. The counteranion plays an important role in both the activity and selectivity. These catalysts constitute an alternative to those based on toxic and expensive late-transition metals. [source] Synthesis of ethylene/propylene elastomers containing a terminal reactive group: The combination of metallocene catalysis and control chain transfer reactionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2005U. Kandil Abstract This article discusses a chemical route to prepare new ethylene/propylene copolymers (EP) containing a terminal reactive group, such as ,-CH3 and OH. The chemistry involves metallocene-mediated ethylene/propylene copolymerization in the presence of a consecutive chain transfer agent,a mixture of hydrogen and styrene derivatives carrying a CH3 (p -MS) or a silane-protected OH (St-OSi). The major challenge is to find suitable reaction conditions that can simultaneously carry out effective ethylene/propylene copolymerization and incorporation of the styrenic molecule (St-f) at the polymer chain end, in other words, altering the St-f incorporation mode from copolymerization to chain transfer. A systematic study was conducted to examine several metallocene catalyst systems and reaction conditions. Both [(C5Me4)SiMe2N(t -Bu)]TiCl2 and rac-Et(Ind)2ZrCl2, under certain H2 pressures, were found to be suitable catalyst systems to perform the combined task. A broad range of St-f terminated EP copolymers (EP- t -p-MS and EP- t -St-OH), with various compositions and molecular weights, have been prepared with polymer molecular weight inversely proportional to the molar ratio of [St-f]/[monomer]. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1858,1872, 2005 [source] Styrene/substituted styrene copolymerization by Ph2Zn,metallocene,MAO systems: homo- and copolymerization of p -methoxystyrene with styrene,POLYMER INTERNATIONAL, Issue 5 2008Franco M Rabagliati Abstract BACKGROUND: The present work is part of a general study regarding the homo- and copolymerization of styrene using diphenylzinc,additive initiator systems, with the aim of improving the properties of commercial atactic polystyrene. The study is focused on syndiotactic polystyrene and/or copolymers of styrene (S) with substituted styrene, styrene derivatives or various ,-olefins. This research has been ongoing over the last 15 years. RESULTS: The reported experiments show that binary metallocene,methylaluminoxane (MAO) and ternary Ph2Zn,metallocene,MAO, depending on the metallocene employed, are capable of inducing both homo- and copolymerization of styrene and p -methoxystyrene (p -MeOS). The results indicate that for a styrene/p -MeOS mole ratio with p -MeOS > 25% the product obtained has only a minor incorporation of styrene units. The efficiency of the metallocenes studied follows the order bis(n -butylcyclopentadienyl)titanium dichloride ((n -BuCp)2TiCl2) > indenyltitanium trichloride (IndTiCl3) > Cp2TiCl2. CONCLUSION: Metallocenes (n -BuCp)2TiCl2, Cp2TiCl2 and IndTiCl3 in binary systems combined with MAO, as well as in ternary systems combined with Ph2Zn and MAO, induce the homopolymerization of p -MeOS and its copolymerization with styrene. The styrene/p -MeOS copolymer obtained was enriched in p -MeOS with respect to the initial feed, in agreement with the I+ inductive effect of the methoxy group in the para position of styrene. As already reported, the role of Ph2Zn was nullified by its complexation with the p -MeOS comonomer. Copyright © 2008 Society of Chemical Industry [source] Modular Chiral Bidentate Phosphonites: Design, Synthesis, and Application in Catalytic Asymmetric Hydroformylation ReactionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2008Baoguo Zhao Dr. Abstract A new class of C2 -symmetric chiral bidentate phosphonite ligands has been synthesized in moderate to good yields from readily available starting materials. Application of these air-stable chiral phosphonites in the RhI -catalyzed asymmetric hydroformylation of styrene derivatives, vinyl acetate, and allyl cyanide afforded the corresponding chiral aldehydes with high regio- and enantioselectivities under mild reaction conditions. The modular nature of the ligands allows fine-tuning of the selectivities through judicious modifications of the substituents on the ligand backbone. X-ray structural analysis of the catalyst precursor suggested that the steric hindrance caused by the protruding remote substituents of the ligands into the vicinity of the metal center might be an important factor for the enantio-control of the reaction, whereas the sense of asymmetric induction can be rationalized on the basis of a trigonal-bipyramidal transition state diagram. [source] Asymmetric Epoxidation of Terminal Olefins with Binaphthyl Strapped Porphyrin Catalysts: (-( Stacking Interaction and Steric Effects on the EnantioselectivitiesCHINESE JOURNAL OF CHEMISTRY, Issue 5 2009Qizhi REN Abstract Two binaphthyl strapped porphyrins with similar chiral auxiliaries 1b and 2b were used as efficient catalysts for asymmetric epoxidation of both styrene derivatives and non-aromatic olefin substrates. Theoretical calculation of styrene approach to both catalysts has been performed. The subtle difference of the chiral cavities between two porphyrins has been analyzed by 1H NMR. The ,-, stacking interaction between aromatic substrates and catalysts might be one factor for the dramatic different enantioselectivities. Besides, the steric effect of the binaphthyl handle of 1b and 2b also causes the high ee values for non-aromatic olefin epoxidations. [source] | |||||||||||||||||||||||||