Natural deep eutectic solvents as an efficient and reusable active system for the Nazarov cyclization

Nejrotti, Stefano; Iannicelli, Marta; Jamil, Salwa Simona; Arnodo, Davide; Blangetti, Marco; Prandi, Cristina

doi:10.1039/c9gc03465j

Cited by 46 publications

(34 citation statements)

References 90 publications

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“…Upon ultrafiltration to separate the acetate, the secondary product of this reaction, it is possible to evaporate the water and reuse the DES, as it has been recently shown for similar DESs. 51 …”

Section: Resultsmentioning

confidence: 99%

Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization

Vicente

Huš

Likozar

et al. 2021

ACS Sustainable Chem. Eng.

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Chitin is the most abundant marine biopolymer, being recovered during the shell biorefining of crustacean shell waste. In its native form, chitin displays a poor reactivity and solubility in most solvents due to its extensive hydrogen bonding. This can be overcome by deacetylation. However, this process requires a high concentration of acids or bases at high temperatures, forming large amounts of toxic waste. Herein, we report on the first deacetylation with deep eutectic solvents (DESs) as an environmentally friendly alternative, requiring only mild reaction conditions. Biocompatible DESs are efficient in disturbing the native hydrogen-bonding network of chitin, readily dissolving it. First, quantum chemical calculations have been performed to evaluate the feasibility of different DESs to perform chitin deacetylation by studying their mechanism. Comparing these with the calculated barriers for garden-variety alkaline/acidic hydrolysis, which are known to proceed, prospective DESs were identified with barriers around 25 kcal·mol –1 or lower. Based on density functional theory results, an experimental screening of 10 distinct DESs for chitin deacetylation followed. The most promising DESs were identified as K 2 CO 3 :glycerol (K 2 CO 3 :G), choline chloride:acetic acid ([Ch]Cl:AA), and choline chloride:malic acid ([Ch]Cl:MA) and were subjected to further optimization with respect to the water content, process duration, and temperature. Ultimately, [Ch]Cl:MA showed the best results, yielding a degree of deacetylation (DDA) of 40% after 24 h of reaction at 120 °C, which falls slightly behind the threshold value (50%) for chitin to be considered chitosan. Further quantum chemical calculations were performed to elucidate the mechanism. Upon the removal of 40% N -acetyl groups from the chitin structure, its reactivity was considerably improved.

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Section: Resultsmentioning

confidence: 99%

Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization

Vicente

Huš

Likozar

et al. 2021

ACS Sustainable Chem. Eng.

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“…Natural deep eutectic solvents (often referred to as NADES [ 17 , 18 ]) are perhaps even more appealing, as the components are derived from bio-sourced and/or renewable feedstocks. The applications of DES systems are diverse given their unique properties, and have seen application in numerous areas including metal nanoparticle synthesis [ 19 ], carbon dioxide fixation [ 20 ], modification [ 21 ] and solubilization [ 22 ] of cellulose, RNA extraction [ 23 ], preparation and modification of polymer membranes [ 24 , 25 ], electrolytes for fuel cells [ 26 , 27 ], natural product extraction [ 28 ] and a wide array of chemical syntheses [ 29 , 30 , 31 , 32 ]. The reader is directed to several excellent reviews detailing the use of DES systems in various areas of chemistry and chemical engineering [ 33 , 34 , 35 , 36 , 37 , 38 , 39 ].…”

Section: Introductionmentioning

confidence: 99%

Greener, Faster, Stronger: The Benefits of Deep Eutectic Solvents in Polymer and Materials Science

2021

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Deep eutectic solvents (DESs) represent an emergent class of green designer solvents that find numerous applications in different aspects of chemical synthesis. A particularly appealing aspect of DES systems is their simplicity of preparation, combined with inexpensive, readily available starting materials to yield solvents with appealing properties (negligible volatility, non-flammability and high solvation capacity). In the context of polymer science, DES systems not only offer an appealing route towards replacing hazardous volatile organic solvents (VOCs), but can serve multiple roles including those of solvent, monomer and templating agent—so called “polymerizable eutectics.” In this review, we look at DES systems and polymerizable eutectics and their application in polymer materials synthesis, including various mechanisms of polymer formation, hydrogel design, porous monoliths, and molecularly imprinted polymers. We provide a comparative study of these systems alongside traditional synthetic approaches, highlighting not only the benefit of replacing VOCs from the perspective of environmental sustainability, but also the materials advantage with respect to mechanical and thermal properties of the polymers formed.

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“…The availability of one of the two components to act in a catalytic role is dependent on the "freedom" of one component from the counterpart in the liquid structure; this effect has an impact on the pKa value of acids, that showed different behaviors when mixed in DESs' structures. [34,35,39,40] In this work, it is reported the use of a set of differently structured NADESs as "active" and green reaction media in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc).…”

Section: Introductionmentioning

confidence: 99%

Investigation of Base-free Copper-Catalysed Azide–Alkyne Click Cycloadditions (CuAAc) in Natural Deep Eutectic Solvents as Green and Catalytic Reaction Media

Giofrè¹,

Tiecco²,

Ferlazzo³

et al. 2021

Preprint

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<p>The click cycloaddition reaction of azides and alkynes affording 1,2,3-triazoles is a widely used and effective chemical transformation, applied to obtain relevant products in medicine, biology and materials science. In this work, a set of Natural Deep Eutectic Solvents (NADESs) as green and “active” reaction media, has been investigated in the copper-catalysed azide–alkyne cycloaddition reactions (CuAAc). The use of these innovative solvents has shown to improve the reaction effectiveness, giving excellent yields. NADESs proved to be “active” in these transformations for the absence of added bases in all the performed reactions and in several cases, for their reducing capabilities. The reactions outcomes were rationalized by DFT calculations which demonstrated the involvement of H-bonds between DESs and alkynes as well as a stabilization of copper catalytic intermediates. The green experimental conditions, namely the absence of a base, the low temperatures, the lowering of reagents and the possibility of recycling of the green solvents, outline the great potential of NADESs for CuAAc and in general, for green organic synthesis. </p>

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Natural deep eutectic solvents as an efficient and reusable active system for the Nazarov cyclization

Abstract: The Nazarov cyclization was successfully performed in acidic NaDESs with full recyclability and scalability.

Cited by 46 publications

References 90 publications

Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization

Chitin Deacetylation Using Deep Eutectic Solvents: Ab Initio-Supported Process Optimization

Greener, Faster, Stronger: The Benefits of Deep Eutectic Solvents in Polymer and Materials Science

Investigation of Base-free Copper-Catalysed Azide–Alkyne Click Cycloadditions (CuAAc) in Natural Deep Eutectic Solvents as Green and Catalytic Reaction Media

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