نتایج جستجو برای: Phosphorus ylides

تعداد نتایج: 42142  

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه شهید باهنر کرمان - دانشکده شیمی 1391

ایلیدهای فسفر ترکیبات فعالی هستند دربسیاری از واکنش های با ارزش سنتز ترکیبات آلی شرکت میکنند ودارای کاربردهای سنتزی بسیار زیادی در زمینه های بیولوژیکی،دارویی وصنعتی می باشند.این ترکیبات بدلیل ساده بودن روش تهیه وهمچنین بواسطه فعالیت بسیاربالا در بسیاری از واکنشگرهاونیز راندمان بالای محصول ،ترکیبات ایده الی دربسیاری از زمینه ها می باشند

2012
David W. Allen

The cis-trans ratio of the alkenes formed in Wittig reactions of semistabilised ylides (derived from benzyltriarylphosphonium salts in ethanolic sodium ethoxide) with benzaldehyde, acetaldehyde or trimethylacetaldehyde increases as steric crowding at phosphorus increases. In contrast, the cis-trans ratio of the unsaturated esters formed in the related reactions of the stabilised ethoxycarbonylm...

Journal: :Chemical communications 2006
Chuan-Ying Li Xiu-Li Sun Qing Jing Yong Tang

Pseudo-C2-symmetric chiral phosphorus ylides have been designed and synthesized for the enantioselective preparation of allenic esters, and up to 92% ee has been achieved.

Journal: :European Journal of Organic Chemistry 2019

2013
Fouad M. Soliman Medhat M. Said

The reaction o f 1-hydroxyxanthenone (1) and hydroxyquinoline (10, 13) Mannich bases with the reactive phosphacumulated ylides (2), represents a new way for the synthesis o f the pyranones and pyranthiones (5, 11, 14). On the other hand, the stabilized phosphorus ylides (6) affect the transylidation o f the Mannich base (1) to the corresponding phosphoranylidenes (9). The structure o f the resu...

Journal: :Beilstein Journal of Organic Chemistry 2005
Stephen P Marsden Pascal C Ducept

BACKGROUND Allenylsilanes are useful intermediates in organic synthesis. An attractive, convergent but little used approach for their synthesis is the alkylidenation of stable silylketenes. Reactions thus far have been limited to the use of unsubstituted silylketenes (or equivalents) with stabilised or semi-stabilised ylides only. The current study explores the reactions of substituted ketenes ...

Journal: :Journal of the American Chemical Society 2002
Viktor P Balema Jerzy W Wiench Marek Pruski Vitalij K Pecharsky

We describe the nearly quantitative preparation of phosphorus ylides and the Wittig reaction occurring in the solid sate during high-energy mechanochemical processing. Initial insights into the details of the discovered chemical transformations indicate that high-energy mechanical processing supports the interaction of reacting centers by breaking crystallinity of the reactants and by providing...

Journal: :Chemical communications 2013
Yi-Ling Tsai Yu-Shiou Fan Chia-Jui Lee Chan-Hui Huang Utpal Das Wenwei Lin

Preparation of new types of trisubstituted oxazoles is realized via chemoselective O-acylations and intramolecular Wittig reactions with ester functionalities using in situ formed phosphorus ylides as key intermediates. A plausible reaction mechanism for this undiscovered chemistry is also proposed based on the existence of expected and rearranged isomeric oxazoles.

Journal: :Chemical communications 2014
Mei Yang Tianyi Wang Shixuan Cao Zhengjie He

Phosphine-catalyzed [4+1] annulation of electron-deficient 1,3-dienes or 1,3-azadienes with maleimides has been successfully developed under very mild conditions, providing a convenient and highly efficient method for constructing 2-azaspiro[4.4]nonenes and 1,7-diazaspiro[4.4]nonenes. This reaction represents the first example of [4+1] cyclization between electron-deficient 4π-conjugated system...

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