نتایج جستجو برای: Olefin

تعداد نتایج: 2960  

Traditional systems for olefin/paraffin separation, like low-temperature distillation, are expensive and very energy consuming, and therefore, alternative separation methods are desired. Facilitated transport membranes are new tools for this separation to be substituted in large scale separation of olefin-paraffin mixtures. To design a membrane process for olefin-paraffin separation, equilibriu...

Journal: :Journal of the American Chemical Society 2005
Soon Hyeok Hong Daniel P Sanders Choon Woo Lee Robert H Grubbs

1,4-Benzoquinones have been found to prevent olefin isomerization of a number of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed olefin metathesis reactions. Electron-deficient benzoquinones are the most effective additives for the prevention of olefin migration. This mild, inexpensive, and effective method to block olefin isomerization increases the synthetic utility...

2016
Saner Poplata Andreas Tröster You-Quan Zou Thorsten Bach

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 2...

2001
Edward T. Zellers Guo-Zheng Zhang

Certain olefin gases and vapors can be measured selectively at low concentrations using surface acoustic wave (SAW) sensors vated with reagents of the general formula trans-PtClz(olefin)(amine). The sensor response depends on the steady-state rate of mass change associated with substitution of the initially complexed olefin by the free olefin analyte. This paper examines the effects of changes ...

2017
T. Patrick Montgomery Adam M. Johns Robert H. Grubbs

Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three categories of Z-selective olefin metathesis catalysts has made Z-ole...

Journal: :journal of membrane science and research 0
maryam takht ravanchi department of chemical engineering, amirkabir university of technology (tehran polytechnic), no. 424, hafez ave., p.o. box 15875- 4413, tehran, iran tahereh kaghazchi department of chemical engineering, amirkabir university of technology (tehran polytechnic), no. 424, hafez ave., p.o. box 15875- 4413, tehran, iran ali kargari membrane processes laboratory, department of petrochemical engineeing, amirkabir university of technology, mahshahr campus, mahshar, iran

traditional systems for olefin/paraffin separation, like low-temperature distillation, are expensive and very energy consuming, and therefore, alternative separation methods are desired. facilitated transport membranes are new tools for this separation to be substituted in large scale separation of olefin-paraffin mixtures. to design a membrane process for olefin-paraffin separation, equilibriu...

Journal: :Journal of the American Chemical Society 2008
Kurt F Hirsekorn Elliott B Hulley Peter T Wolczanski Thomas R Cundari

The substitution chemistry of olefin complexes (silox)3M(ole) (silox = (t)Bu3SiO; M = Nb (1-ole), Ta (2-ole); ole = C2H4 (as 13C2H4 or C2D4), C2H3Me, C2H3Et, cis-2-C4H8, iso-C4H8, C2H3Ph, cC5H8, cC6H10, cC7H10 (norbornene)) was investigated. For 1-ole, substitution was dissociative (deltaG(double dagger)(diss)), and in combination with calculated olefin binding free energies (deltaG(o)(bind)), ...

Journal: :Journal of the American Chemical Society 2012
Alexander P Pulis Varinder K Aggarwal

Enantioenriched secondary allylic carbamates have been deprotonated with sBuLi and reacted with boronic esters. In contrast to other electrophiles, high α-selectivity was observed and the boronate complexes were formed with almost complete retention of stereochemistry. The boronate complexes underwent a stereospecific 1,2-migration leading to tertiary allylic boronic esters with high er (>98:2)...

Journal: :Organic letters 2016
Adam M Johns Tonia S Ahmed Bradford W Jackson Robert H Grubbs Richard L Pederson

The first kinetically controlled, highly trans-selective (>98%) olefin cross-metathesis reaction is demonstrated using Ru-based catalysts. Reactions with either trans or cis olefins afford products with highly trans or cis stereochemistry, respectively. This E-selective olefin cross-metathesis is shown to occur between two trans olefins and between a trans olefin and a terminal olefin. Addition...

2017
Youai Qiu Bin Yang Can Zhu Jan-E. Bäckvall

A highly selective olefin-assisted palladium-catalyzed oxidative carbocyclization via remote olefin insertion to afford cyclohexenes has been developed. It was shown that the assisting olefin moiety was indispensable for the formation of the cyclohexene product. Furthermore, preliminary studies on chiral anion-induced asymmetrical carbocyclization-borylation of enallenes have been carried out.

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