lewis acid catalysts
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2021 ◽  
Author(s):  
Pelin Ulukan ◽  
Saron Catak ◽  
Erdal Ertas

Stilbenes substituted with –CN, –OMe and –Br were synthesized using four different Lewis acid catalysts and their reaction efficiencies were compared. In addition to McMurry reagents known in literature, a more familiar and economical catalyst ZnCl2 was used for the first time in our reaction procedures. Furthermore, bromine substituted stilbenes were subjected to Suzuki coupling reactions to append a triphenylamine (TPA) unit, which enhances fluorescence emissions. Solvatochromic properties of synthesized stilbenes were investigated and aggregation caused quenching (ACQ) properties of TPA containing molecules were systematically examined. Optical properties were also theoretically investigated.


Catalysts ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 5
Author(s):  
Valeria Nori ◽  
Fabio Pesciaioli ◽  
Arianna Sinibaldi ◽  
Giuliana Giorgianni ◽  
Armando Carlone

In the last two decades, boron-based catalysis has been gaining increasing traction in the field of organic synthesis. The use of halogenated triarylboranes as main group Lewis acid catalysts is an attractive strategy. It has been applied in a growing number of transformations over the years, where they may perform comparably or even better than the gold standard catalysts. This review discusses methods of borane synthesis and cutting-edge boron-based Lewis acid catalysis, focusing especially on tris(pentafluorophenyl)-borane [B(C6F5)3], and other halogenated triarylboranes, highlighting how boron Lewis acids employed as catalysts can unlock a plethora of unprecedented chemical transformations or improve the efficiency of existing reactions.


Synthesis ◽  
2021 ◽  
Author(s):  
Zhao-Ying Yang ◽  
Ming Zhang ◽  
Xiao-Chen Wang

The development of chiral borane Lewis acid catalysts opened the door for transition-metal-free catalyzed asymmetric organic reactions. Herein, we have summarized our work on the preparation of two classes of novel chiral bicyclic bisborane Lewis acid catalysts derived from C2-symmetric [3.3.0] dienes and [4.4] dienes, respectively. These catalysts not only form frustrated Lewis pairs with Lewis bases to catalyze asymmetric hydrogenation reactions but also activate Lewis basic functional groups in traditional Lewis acid catalyzed asymmetric reactions.


Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1395
Author(s):  
Cristina Megías-Sayago ◽  
Sara Navarro-Jaén ◽  
Fabien Drault ◽  
Svetlana Ivanova

One of the most trending topics in catalysis recently is the use of renewable sources and/or non-waste technologies to generate products with high added value. That is why, the present review resumes the advances in catalyst design for biomass chemical valorization. The variety of involved reactions and functionality of obtained molecules requires the use of multifunctional catalyst able to increase the efficiency and selectivity of the selected process. The use of glucose as platform molecule is proposed here and its use as starting point for biobased plastics production is revised with special attention paid to the proposed tandem Bronsted/Lewis acid catalysts.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Evan M. Sherbrook ◽  
Matthew J. Genzink ◽  
Bohyun Park ◽  
Ilia A. Guzei ◽  
Mu-Hyun Baik ◽  
...  

AbstractControl over the stereochemistry of excited-state photoreactions remains a significant challenge in organic synthesis. Recently, it has become recognized that the photophysical properties of simple organic substrates can be altered upon coordination to Lewis acid catalysts, and that these changes can be exploited in the design of highly enantioselective catalytic photoreactions. Chromophore activation strategies, wherein simple organic substrates are activated towards photoexcitation upon binding to a Lewis acid catalyst, rank among the most successful asymmetric photoreactions. Herein, we show that chiral Brønsted acids can also catalyze asymmetric excited-state photoreactions by chromophore activation. This principle is demonstrated in the context of a highly enantio- and diastereoselective [2+2] photocycloaddition catalyzed by a chiral phosphoramide organocatalyst. Notably, the cyclobutane products arising from this method feature a trans-cis stereochemistry that is complementary to other enantioselective catalytic [2+2] photocycloadditions reported to date.


2021 ◽  
Author(s):  
Chen Liujuan ◽  
Guowei Zhang ◽  
Jinguang Liu ◽  
Jianye Jiao ◽  
Han Lin ◽  
...  

A four-step synthesis of Remdesivir (1) is presented. This work focuses on the yield improvement of step 1, flow chemistry development of step 2 and 3, process optimization of step 4. The literatures reported (https://dx.doi.org/10.1021/acs.oprd.0c00310 and https://dx.doi.org/10.1021/acs.oprd.0c00172: SI part) step 1 was repeated, but failed in the crystallization, eventually step 1 product was obtained by column chromatography with >98% HPLC purity and 40% IY. The flow chemistry development of step 2(IY: 84%) and 3 (IY: 63%) was achieved and the release of toxic HCN was avoided, the process robustness was improved by flow chemistry. Step 4 was simplified to apply primary alcohol 6 directly (without protection) to react with chiral SM 8. Lewis acid catalysts were screened by HTS and MgI2 gave 50% AY. Cheap and commercially available MgCl2 and NaI were used to replace MgI2, finally Remdesivir (1) was obtained in >99% purity with 40.3% IY.


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