- Co-Polymeric Nanosponges from Cellulose Biomass as Heterogeneous Catalysts for amine-catalyzed Organic Reactions
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Heterogeneous catalysts prepared from biomass waste sources are attracting increasing interest. The reasons rely on the possibility of combining the virtuous approach of circular economy with the consolidated advantages of heterogeneous catalysis, namely the recycling of the system and the possibility to drive selectivity towards desired products. Herein we report a highly porous cellulose-based nanosponge (CNS) and its use as a recoverable catalyst for Henry and Knoevenagel reactions, two classical amino-catalyzed transformations. The material is obtained by cross-linking between TEMPO-oxidized cellulose nanofibers (TOCNF) and branched polyethyleneimine 25 kDa (bPEI) in the presence of citric acid. CNS have been developed as sorbent materials for water remediation but their use as heterogeneous catalysts was never investigated. The fully characterized micro- and nano-porous system guarantees a complete penetration of CNS, allowing reagents to diffuse within. Indeed, by modulating reaction conditions (catalyst loading, temperature, solvent, microwave versus conventional heating, relative ratio of reagents) it was possible to drive selectivity towards the desired products, while maintaining high efficiency in terms of conversion. The catalyst could be re-used several times without losing in catalytic efficiency. In most cases the products’ distribution is quite different from homogeneous conditions, this much more emphasizing the importance of this heterogeneous solution.
- Riva, Laura,Punta, Carlo,Sacchetti, Alessandro
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p. 6214 - 6222
(2020/10/02)
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- Metal free biomimetic deaminative direct C-C coupling of unprotected primary amines with active methylene compounds
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An unprecedented direct C-C coupling reaction of unprotected primary amines with active methylene compounds is reported. The reaction involves a biomimetic deamination of amines which was achieved under conditions free of metallic reagents and strong oxidizing agents. A wide range of primary amines was reacted with different active methylene compounds to provide structurally diverse trisubstituted alkenes and dihydropyridines. A kinetic study revealed an activation barrier of 10.1 kcal mol-1 for the conversion of a key intermediate of the reaction.
- Ghosh, Santanu,Jana, Chandan K.
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supporting information
p. 10153 - 10157
(2019/12/26)
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- Unnatural α-amino ethyl esters from diethyl malonate or ethyl β-bromo-α-hydroxyiminocarboxylate
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We have explored here the scope of the age-old diethyl malonate-based accesses to α-amino esters involving Knoevenagel condensations of diethyl malonate on aldehydes, reductions of the resulting alkylidenemalonates, the preparation of the corresponding α-hydroxyimino esters and their final reduction. This synthetic pathway turned out to be general although some unexpected limitations were encountered. The synthetic modifications of some of the intermediates - using Suzuki-Miyaura coupling or cycloadditions - before undertaking the oximation step - provided accesses to further α-amino esters. Moreover, other pathways to α-hydroxyimino esters were explored including an attempt to improve the cycloadditions between ethyl β-bromo-α-hydroxyiminocarboxylate and various alkylfuranes.
- Coutant, Eloi P.,Hervin, Vincent,Gagnot, Glwadys,Ford, Candice,Baatallah, Racha,Janin, Yves L.
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supporting information
p. 2853 - 2860
(2018/11/26)
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- Knoevenagel condensation catalyzed by a Mexican bentonite using infrared irradiation
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Diethyl malonate undergoes condensation with aromatic aldehydes without solvents, in the presence of a Mexican bentonite using infrared irradiations as the energy source, to give the benzylidenemalonate compounds in fair yield.
- Delgado,Tamariz,Zepeda,Landa,Miranda,Garcia
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p. 753 - 759
(2007/10/02)
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- Synthesis of Helical Molecules Based on 5,6,6a,7,8,12b-Hexahydrobenzophenanthrene-5,8-dione
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Synthetic routes based on Newman'synthesis of a number of polycyclic aromatic hydrocarbons were modified and developed to give a convenient preparation (Scheme 1) of 11 helical molecules formally based on hexalindione (1).In contrast to Newman's work, we
- Cheung, Julie,Field, Leslie D.,Regaglia, Francesca,Sternhell, Sever
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p. 1707 - 1726
(2007/10/03)
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