Green Solvents in Organic Synthesis: An Overview II

Shanab, Karem; Neudorfer, Catharina; Spreitzer, Helmut

doi:10.2174/1385272820666160209212804

Cited by 21 publications

(16 citation statements)

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“…The biomass-derived products are ecofriendly, and they are promising alternative solvents when compared to hazardous solvents. − 2-MTHF is derived from renewable resources by using substrates such as furfural or levulinic acid . The physical and chemical properties of 2-MTHF, such as low miscibility with water, high boiling point, high stability compared to other cyclic-based solvents such as tetrahydrofuran (THF), and others, make it attractive for many synthetic applications.…”

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of 2-Methyltetrahydrofuran behind Reflected Shock Waves over the Temperature Range of 1179–1361 K

2021

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The thermal unimolecular decomposition of 2methyltetrahydrofuran (2-MTHF) was studied behind reflected shock waves in a single-pulse shock tube over the temperature range of 1179−1361 K and pressure range of 9−17 atm. Methane, ethylene, ethane, 1,3-butadiene, propylene, acetaldehyde, and acetylene were identified as products in the decomposition of 2-MTHF. A reaction scheme was proposed to explain the mechanism for the observed products. The experimentally determined rate coefficients were best fit to an Arrhenius expression for the overall decomposition and is represented as k total exp (1179−1361 K) = (3.23 ± 0.59) × 10 11 s −1 exp(−51.3 ± 1.4 kcal mol −1 /RT). Quantum chemistry methods were used to calculate the energetics and kinetics of various possible unimolecular dissociation pathways involved in the thermal decomposition of 2-MTHF. The initial decomposition of 2-MTHF occurs predominantly via ring−methyl (C−CH 3 ) single bond fission, leading to the formation of tetrahydrofuran (C 4 H 7 O) radical, and methyl radical was found to be the major reaction compared to all the possible initial bond fission, ring opening, and molecular elimination channels. The temperature-dependent rate coefficients for the unimolecular dissociation of 2-MTHF were calculated using the RRKM (Rice−Ramsperger−Kassel−Marcus) theory in combination with the CCSD(T)/cc-pVTZ//B3LYP/cc-pVTZ level of electronic structure calculations over the temperature range of 800−1500 K. The computed high-pressure limiting rate coefficients for the initial decomposition of 2-MTHF through C−CH 3 single bond fission channel were found to be ∼2 times higher in the temperatures between 800 and 900 K, and above this temperature, they agree well with the values reported in the literature.

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Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of 2-Methyltetrahydrofuran behind Reflected Shock Waves over the Temperature Range of 1179–1361 K

2021

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“…The Ireland-Claisen rearrangement proceeded in 2-MeTHF with slightly lower yield and very similar diastereoselectivity as in DCM ( Table 5, entries 1 and 2). A low tendency to peroxide formation, stability under acidic and basic conditions, high boiling point, and low heat of vaporization are also positive features of cyclopentyl methyl ether (CpOMe) [40]. From the chemical yield point of view, cyclopentyl methyl ether was the best solvent for the Ireland-Claisen rearrangement of ester 1c; acid 3c was isolated in 84% yield.…”

Section: Resultsmentioning

confidence: 99%

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

Krištofíková¹,

Filo²,

Mečiarová³

et al. 2019

Beilstein J. Org. Chem.

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A range of chiral hydrogen-bond-donating organocatalysts was tested in the Ireland–Claisen rearrangement of silyl ketene acetals. None of these organocatalysts was able to impart any enantioselectivity on the rearrangements. Furthermore, these organocatalysts slowed down the Ireland–Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for reactions involving hydrogen-donating organocatalysts and kinetic experiments suggest that the catalysts bind stronger to the starting silyl ketene acetals than to transition structures thus leading to inefficient rearrangement reactions.

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“…Under the aegis of green chemistry, a mass of research papers proclaim the use of a ‘green’ solvent or the development of a ‘solvent-free’ process (Kerton and Mariott 2013f ; Tanaka and Toda 2000 ). Such research has been usefully summarised by Kerton and Marriott ( 2013a , b , c , d , g ) and others (Welton 2015 ; Clarke et al 2018 ; Shanab et al 2013 , 2016 ; Häckl and Kunz 2018 ; Clark et al 2017a , b ). However, too much published material emphasises claimed benefits (by using the following terms in their titles: green(er); clean(er); benign; environmentally friendly; environmentally benign; environmentally green; environmentally acceptable; eco-friendly; and sustainable) while failing to provide the necessary supporting toxicological or ecotoxicological evidence.…”

Section: Solvents and Sustainabilitymentioning

confidence: 98%

“…Much of this early work has been covered in depth elsewhere (Avalos et al 2006 ; Nelson 2003 ; Capello et al 2007 ; Jessop 2011 ; Leitner et al 2010 ) and brought up to date in recent texts, reviews and articles (Kerton and Marriott 2013a , b , c , d , e , f , g ; Welton 2015 ; Calvo‑Flores et al 2018 ; Clarke et al 2018 ; Shanab et al 2013 ; Shanab et al 2016 ; Häckl and Kunz 2018 ; Clark et al 2017a , b ).…”

Section: Solvents and Sustainabilitymentioning

confidence: 99%

“…It is also pertinent to note that Fig. 2 suggests that reaction media for use in large-scale chemicals production, while significant, is still only a relatively modest fraction of the total solvent usage, despite having been the dominant focus of green chemistry-driven research (Kerton and Marriott 2013a , b , c , d , e , f , g ; Welton 2015 ; Clarke et al 2018 ; Shanab et al 2013 , 2016 ; Häckl and Kunz 2018 ; Clark et al 2017a , b ). A valuable additional perspective is provided by Abbott and Shimizu ( 2019 ) who focus on coatings and adhesives applications, noting the difference between the physicochemical phenomena involved in the processes of dispersion and solubilisation compared with those of dissolution.…”

Section: Solvents and Sustainabilitymentioning

confidence: 99%

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The green solvent: a critical perspective

Winterton

2021

Clean Techn Environ Policy

120

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Solvents are important in most industrial and domestic applications. The impact of solvent losses and emissions drives efforts to minimise them or to avoid them completely. Since the 1990s, this has become a major focus of green chemistry, giving rise to the idea of the ‘green’ solvent. This concept has generated a substantial chemical literature and has led to the development of so-called neoteric solvents. A critical overview of published material establishes that few new materials have yet found widespread use as solvents. The search for less-impacting solvents is inefficient if carried out without due regard, even at the research stage, to the particular circumstances under which solvents are to be used on the industrial scale. Wider sustainability questions, particularly the use of non-fossil sources of organic carbon in solvent manufacture, are more important than intrinsic ‘greenness’. While solvency is universal, a universal solvent, an alkahest, is an unattainable ideal.

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Green Solvents in Organic Synthesis: An Overview II

Cited by 21 publications

References 0 publications

Thermal Decomposition of 2-Methyltetrahydrofuran behind Reflected Shock Waves over the Temperature Range of 1179–1361 K

Thermal Decomposition of 2-Methyltetrahydrofuran behind Reflected Shock Waves over the Temperature Range of 1179–1361 K

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

The green solvent: a critical perspective

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