نتایج جستجو برای: base catalyst

تعداد نتایج: 299630  

2014
Hu Zhang Song Lin Eric N. Jacobsen

Highly enantioselective selenocyclization reactions are promoted by the combination of a new chiral squaramide catalyst, a mineral acid, and an achiral Lewis base. Mechanistic studies reveal that the enantioselectivity originates from the dynamic kinetic resolution of seleniranium ions through anion-binding catalysis.

2016
Madegowda Mahendra

The synthesis of N1 and N2 coumarin substituted 1,2,3-triazole isomers from terminal alkynes, sodium azide, and 4-bromomethylcoumarins in the presence of triethylamine as a base and CuI as a catalyst in good yield are reported. The molecular structure of compounds 3g and 5d are established by single-crystal analysis. GRAPHICAL ABSTRACT ARTICLE HISTORY Received 2 October 2015

2017
Peng Zhou Liang Jiang Fan Wang Kejian Deng Kangle Lv Zehui Zhang

Replacement of precious noble metal catalysts with low-cost, non-noble heterogeneous catalysts for chemoselective reduction and reductive coupling of nitro compounds holds tremendous promise for the clean synthesis of nitrogen-containing chemicals. We report a robust cobalt-nitrogen/carbon (Co-N x /C-800-AT) catalyst for the reduction and reductive coupling of nitro compounds into amines and th...

2017
Ken-Lin Chang Yuan-Chung Lin Lee Cheng Shang-Cyuan Chen Sung-Yuan Mao Cláudia Gomes Silva

In this study, a nano-Ca(OH)2/Fe3O4 catalyst was used to produce biodiesel from a 1:1 mixed jatropha-castor oil. By loading Ca(OH)2 onto Fe3O4 nanoparticles, it increased the specific surface area by almost 40%, which improved the catalytic activity as it provided a larger area for the reactants to interact. The main purpose of mixing jatropha oil with castor oil was to lower the viscosity of t...

Journal: :Chemical communications 2013
Lina Xu Shugui Hua Shuhua Li

Density functional theory investigations reveal that a cavitand with an introverted aldehyde group not only provides the host-guest interaction for preorganizing the substrate and stabilizing the hemiaminal intermediate, but also acts as an acid/base catalyst in the subsequent dehydration step in its reaction with a primary amine.

Journal: :Chemical communications 2012
Ping Li Chang-Yan Cao Zhe Chen Hua Liu Yu Yu Wei-Guo Song

A core-shell structured mesoporous silica nanosphere with antagonistic acid and basic sites spatially isolated and designated diffusion path was fabricated and served as an efficient acid-base bifunctional catalyst for one-pot cascade reaction sequences with excellent activity and selectivity.

2017
Lei Yang Romain Melot Markus Neuburger Olivier Baudoin

The first efficient palladium(0)-catalyzed enantioselective C(sp)–H activation reaction using a catalytic chiral base and an achiral phosphine ligand is reported. Fine-tuning the binol-derived phosphoric acid pre-catalyst and the reaction conditions was found to be crucial to achieve high levels of enantioselectivity for a variety of indoline products containing both triand tetrasubstituted ste...

Journal: :Chemical communications 2006
Stefan van Dommele Krijn P de Jong Johannes H Bitter

Nitrogen-containing carbon nanotubes (NCNT) are effective re-usable solid base catalysts, their activity for a Knoevenagel condensation being related to the amount of pyridinic nitrogen incorporated in the NCNT structure, which could be tuned by the synthesis parameters of the catalyst.

Journal: :Molecules 2011
Edyta Gondela Krzysztof Z Walczak

3,4-Dichloro-5-hydroxy-2(5H)-furanone treated with methyl chloroformate in the presence of diisopropylethylamine (Hünig's base) gave the corresponding carbonate. The labile methoxycarbonyloxy group smoothly undergoes substitution by amino alcohols. The obtained 5-(w-hydroxyalkylamino) mucochloric acid derivatives reacted with peracetylated glucals using triphenylphosphine hydrobromide as a cata...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه بیرجند - دانشکده علوم 1391

در قسمت اول این تحقیق، کمپلکس [fe-schiff base] با روش اشباع سازی در نانوراکتورsba-15 تثبیت شده است. این نانو کاتالیزور به وسیله تکنیک هایxrd ،tem ، bet (جذب – واجذب نیتروژن(، ir، uv و tga شناسایی شده اند. الگوی xrd و تصویر tem مربوط به [fe-schiff base/sba-15] ساختار هگزاگونال منظم را در مزوحفره های سیلیکا نشان دادند. ایزوترم جذب – واجذب نیتروژن [fe-schiff base/sba-15] بر طبق دسته بندی آیوپاک بر...

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