Diaryliodonium salts as efficient Lewis acid catalysts for direct three component Mannich reactions

RSC Advances ◽  
2015 ◽  
Vol 5 (32) ◽  
pp. 25485-25488 ◽  
Author(s):  
Yanxia Zhang ◽  
Jianwei Han ◽  
Zhen-Jiang Liu
Keyword(s):  
Lewis Acid ◽  
Mannich Reaction ◽  
Solvent Free ◽  
Acid Catalysts ◽  
Lewis Acid Catalysts ◽  
Mannich Reactions ◽  
Highly Active ◽  
Diaryliodonium Salts ◽  
Solvent Free Conditions

Diaryliodonium(iii) salts, as highly active and versatile Lewis acid catalysts for the direct three component Mannich reaction under solvent free conditions, have been investigated.

Hydrothermal synthesis of Sn-Beta zeolites in F−-free medium

2018 ◽  
Vol 5 (11) ◽  
pp. 2763-2771 ◽  
Author(s):  
Hao Xu ◽  
Xudong Wang ◽  
Peng Ji ◽  
Haihong Wu ◽  
Yejun Guan ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Lewis Acid ◽  
Crystal Size ◽  
Acid Catalysts ◽  
Free Medium ◽  
Lewis Acid Catalysts ◽  
Structure Directing Agent ◽  
Highly Active ◽  
Beta Zeolites

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.

Metal-Free Living Cationic Polymerization Using Diaryliodonium Salts as Organic Lewis Acid Catalysts

2020 ◽  
Vol 53 (11) ◽  
pp. 4185-4192
Author(s):  
Rui Haraguchi ◽  
Tsuyoshi Nishikawa ◽  
Arihiro Kanazawa ◽  
Sadahito Aoshima
Keyword(s):  
Lewis Acid ◽  
Cationic Polymerization ◽  
Acid Catalysts ◽  
Lewis Acid Catalysts ◽  
Free Living ◽  
Metal Free ◽  
Living Cationic Polymerization ◽  
Diaryliodonium Salts

scholarly journals Tin-containing silicates: structure–activity relations

2012 ◽  
Vol 468 (2143) ◽  
pp. 2000-2016 ◽  
Author(s):  
Christian M. Osmundsen ◽  
Martin Spangsberg Holm ◽  
Søren Dahl ◽  
Esben Taarning
Keyword(s):  
Lewis Acid ◽  
Active Site ◽  
Low Temperatures ◽  
Acid Strength ◽  
Acid Catalysts ◽  
Lewis Acid Catalysts ◽  
Highly Active ◽  
Structure Activity ◽  
Structure Activity Relations ◽  
Mcm 41

The selective conversion of biomass-derived substrates is one of the major challenges facing the chemical industry. Recently, stannosilicates have been employed as highly active and selective Lewis acid catalysts for a number of industrially relevant reactions. In the present work, four different stannosilicates have been investigated: Sn-BEA, Sn-MFI, Sn-MCM-41 and Sn-SBA-15. When comparing the properties of tin sites in the structures, substantial differences are observed. Sn-beta displays the highest Lewis acid strength, as measured by probe molecule studies using infrared spectroscopy, which gives it a significantly higher activity at low temperatures than the other structures investigated. Furthermore, the increased acid strength translates into large differences in selectivity between the catalysts, thus demonstrating the influence of the structure on the active site, and pointing the way forward for tailoring the active site to the desired reaction.

scholarly journals Pt/CeO2 with residual chloride as reusable soft Lewis acid catalysts: application to highly efficient isomerization of allylic esters

2021 ◽  
Author(s):  
Qi-An Huang ◽  
Asahi Haruta ◽  
Yuhya Kumamoto ◽  
Haruno Murayama ◽  
Eiji Yamamoto ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Lewis Acid ◽  
High Catalytic Activity ◽  
Acid Catalysts ◽  
Lewis Acid Catalysts ◽  
X Ray ◽  
Solvent Free Conditions ◽  
Highly Dispersed ◽  
Silica Alumina ◽  
Allylic Esters

Abstract Heterogeneous acid and base catalysts play a crucial role in many important chemical processes. Hard Lewis and Brønsted acid catalysts like silica-alumina and zeolites have been widely applied in numerous reactions; however, developing reusable and active soft Lewis acid catalysts remain a challenge. Herein, we demonstrate for the first time that a highly dispersed supported platinum catalyst can act as a heterogeneous soft Lewis acid. High turnover numbers and reusability were observed in the isomerization of allylic esters under solvent-free conditions. Moreover, the as-prepared catalysts are characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) analyses, revealing that the highly dispersed Pt clusters with Pt–Cl bonds play a key role in the high activity. The residual chloride anion enhances the Lewis acidity of the Pt metal center and thus improves the catalytic activity. Simultaneously, the high catalytic activity of Pt/CeO2 with residual chloride and the soft Lewis acid mechanism are also proved by density functional theory (DFT) calculations based on the model reaction.

Urea-Catalyzed Functionalization of Unactivated C–H Bonds

2020 ◽  
Author(s):  
Alex L. Bagdasarian ◽  
Stasik Popov ◽  
Benjamin Wigman ◽  
Wenjing Wei ◽  
woojin lee ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Organic Synthesis ◽  
High Energy ◽  
Acid Catalysts ◽  
Potential Utility ◽  
New Paradigm ◽  
Lewis Acid Catalysts ◽  
Reaction Conditions ◽  
Highly Active ◽  
Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp<sup>2</sup> carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.<br>

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