scholarly journals Catalytic Allylic Chlorination of Natural Terpenic Olefins Using Supported and Nonsupported Lewis Acid Catalysts

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Ayoub Abdelkader Mekkaoui ◽  
Mouhsine Laayati ◽  
Hamza Orfi ◽  
Larbi El Firdoussi ◽  
Soufiane El Houssame

A mild and convenient method for the allylic chlorination of naturally occurring terpenic olefins was investigated in the presence of different supported and non-supported Lewis acid catalysts. The reaction has been tested on carvone as a model substrate in the presence of sodium hypochlorite as chlorine donor. The scope and limitations of transition metal-based Lewis acid catalysts, stoichiometry, and substrate structure were evaluated. Among the iron precursors used, FeCl3 and FeCl2 provide the promise of a general approach to allylic or vinylic chlorination reaction. Various terpenic olefins were examined in the presence of FeCl3/NaOCl combination system. The catalytic chlorination proceeds under mild conditions with short reaction time and shows a high selectivity affording the corresponding chlorides in good to excellent yields.

2005 ◽  
Vol 70 (11) ◽  
pp. 1943-1952 ◽  
Author(s):  
Ramandeep Kaur Vohra ◽  
Jean-Luc Renaud ◽  
Christian Bruneau

The direct condensation of amines with β-ketoesters and β-diketones to produce functional enamine derivatives has been investigated with zinc Lewis acid catalysts. Zn(OAc)2·2H2O shows good catalytic activity and leads to a chemo- and stereoselective formation of (Z)-enamine derivatives from aliphatic primary amines and ring-substituted anilines under mild conditions.


2019 ◽  
Author(s):  
David J. Fortman ◽  
Daylan T. Sheppard ◽  
William Dichtel

<div> <div> <div> <p>The reprocessing or recycling of cross-linked polymers by incorporating dynamic covalent cross- links has the potential to increase their usable lifetimes and reduce their environmental impact. Polyurethanes (PUs) are the largest class of cross-linked polymers; however, their direct recycling into similar value materials is not well-developed. We demonstrate that several Lewis acid catalysts mediate urethane exchange selectively and under mild conditions. Incorporating these catalysts into cross-linked polyether and polyester PUs with structures similar to commercial PU thermosets gives cross-linked materials that can completely relax stress in 100 seconds at temperatures as low as 140 oC. The dynamic polymers were reprocessed via compression molding to provide materials with similar cross-linking densities to as-synthesized materials. Because these systems are based on commercially available PU monomers and inexpensive Lewis acid catalysts, we anticipate that these findings will enable the recycling of traditional thermosetting PUs. </p> </div> </div> </div>


2019 ◽  
Author(s):  
David J. Fortman ◽  
Daylan T. Sheppard ◽  
William Dichtel

<div> <div> <div> <p>The reprocessing or recycling of cross-linked polymers by incorporating dynamic covalent cross- links has the potential to increase their usable lifetimes and reduce their environmental impact. Polyurethanes (PUs) are the largest class of cross-linked polymers; however, their direct recycling into similar value materials is not well-developed. We demonstrate that several Lewis acid catalysts mediate urethane exchange selectively and under mild conditions. Incorporating these catalysts into cross-linked polyether and polyester PUs with structures similar to commercial PU thermosets gives cross-linked materials that can completely relax stress in 100 seconds at temperatures as low as 140 oC. The dynamic polymers were reprocessed via compression molding to provide materials with similar cross-linking densities to as-synthesized materials. Because these systems are based on commercially available PU monomers and inexpensive Lewis acid catalysts, we anticipate that these findings will enable the recycling of traditional thermosetting PUs. </p> </div> </div> </div>


2018 ◽  
Vol 5 (11) ◽  
pp. 2763-2771 ◽  
Author(s):  
Hao Xu ◽  
Xudong Wang ◽  
Peng Ji ◽  
Haihong Wu ◽  
Yejun Guan ◽  
...  

Sn-Beta zeolites, with high Sn content and smaller crystal size, hydrothermally synthesized in F−-free medium using N-cyclohexyl-N,N-dimethylcyclohexanaminium hydroxide as the structure-directing agent with the assistance of Na+ and seed, are highly active as Lewis acid catalysts.


2003 ◽  
Vol 17 (10) ◽  
pp. 795-799 ◽  
Author(s):  
Yasuo Imakura ◽  
Satoru Nishiguchi ◽  
Akihiro Orita ◽  
Junzo Otera

ChemInform ◽  
2013 ◽  
Vol 44 (40) ◽  
pp. no-no
Author(s):  
Jeanne-Marie Begouin ◽  
Meike Niggemann

Sign in / Sign up

Export Citation Format

Share Document