1,721,117 research outputs found
DIALKYL CARBONATE CHEMISTRY: EXPLORING NEW GREEN, CHLORINE-FREE SYNTHETIC APPROACHES
Full text linkDialkyl carbonates are green solvents and reagents (DACs) extensively investigated as possible alternatives to
chlorine reagents and solvents.[1] Specific areas where Green, chlorine-free synthetic approaches via DAC
chemistry have been exploited include:
Renewables upgrade: Substitution of petroleum-based compounds with renewable substances has been a
focal point in recent research. The US Department of Energy (DOE) has published a list of target molecules
considered of special interest for biorefinery development.[2] Among them D-sorbitol, and HMF derivatives
occupies a top position in the list as they encompass all of the desired criteria for a bio-based platform
compound. In particular, chlorine-free upgrading of D-sorbitol, isosorbide and HMF with DACs has led to
several industrially relevant product.[2]
Heterocycles: DACs chemistry has been proved efficient in the preparation of numerous 5- and 6-membered
heterocycles including: furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines and
cyclic carbamates. In these reactions, the selected DAC acts as sacrificial molecule instead of Chlorine-based
compounds.[3] Mustard carbonates:
Mustard carbonate: Carbonate analogues of toxic mustard gases - are a new class of compounds, easily
synthesized via DAC chemistry retaining the reactivity of mustard gases, but that are not toxic for the operators
or the environment. Their reactivity as novel, green electrophiles and their possible potential application as
green reagents have been investigated; applications include synthesis of heterocycles via ring expansion and
macromolecules preparation.[4]
Research conducted in the abovemention areas indicate that DACs can be used to develop a beyond chlorine
chemistry with high efficiency and selectivity
Chlorine-free chemistry via dialkyl carbonates
No full textIn the last decades, due to the increasingly stringent environmental regulations, companies’ priority has become the conservation of high process performances by means of eco-compatible methodologies. In this view, green solvents and reagents dialkyl carbonates (DACs) have been extensively investigated as possible alternatives to some chlorine reagents (methyl and acyl halides, phosgene) and solvents (dichloromethane and chloroform).
In this talk the following aspects and applications of chlorine-free chemistry via DAC will be addressed:
Heterocycles synthesis: DACs chemistry has been proved efficient in the preparation of numerous 5- and 6-membered heterocycles including: furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines and cyclic carbamates. In these reactions, the selected DAC acts as sacrificial molecule being completely converted, at the end of the reaction, into CO2 and an alcohol. Chlorine and carbonate moieties can both be used as sacrificial groups in nucleophilic displacements, however the latter do not produce salts and harmful wastes to be disposed of and display low toxicity and high biodegradability.
Renewables upgrade: The reactivity of isosorbide with DMC is an industrially relevant process as it can lead to the formation of dicarboxymethyl isosorbide, a potential monomer for isosorbide-based polycarbonate, and dimethyl isosorbide, a high boiling green solvent. The peculiar reactivity of isosorbide via chlorine-free DMC-based approaches is paving the way to several industrial potential applications.
From war chemicals to green reagents: Mustard gases are vesicant and blistering agents that have been sadly used in several chemical warfare. The toxicity of these compounds is strictly related to their high reactivity. Sulfur and nitrogen (half-)mustard carbonate analogues are a new class of compounds, easily synthesized via DAC chemistry retaining the reactivity of mustard gases, but that are not toxic for the operators or the environment. Their reactivity as novel, green electrophiles and their possible potential application as green reagents will be discussed
Synthesis and derivatization of 2,5-bis(hydroxymethyl)furan (BHMF)
No full textBiomass-derived C6-furanic platform chemicals are regarded as the most promising building blocks in biorefinery exploitation. 5-Hydroxymethylfurfural (HMF) is referred as a “sleeping giant” in consideration of its potential in bridging the gap from a fossil-based chemistry to a more sustainable one. HMF is a versatile substrate with enormous market potential as it can be easily converted into high value chemicals, materials and bio-based polymers.[1] However, there are some limitations in developing an efficient HMF-based chemistry, i.e., its preferred solubility in water rather than in organic solvents, the absence of a cost-efficient scale-up synthesis, and well know HMF stability issue partially solved by the addition of small amount of specific stabilizers.
In our laboratory we have developed a new approach to HMF from D-Fructose using dimethyl carbonate as an extracting solvent in the presence of an acidic heterogenous catalyst. This synthesis is easily scalable up to 20 grams of D-fructose and allows to recover HMF in 70% isolated yield.[2] Quick reduction of HMF to the related 2,5-bis(hydroxymethyl)furan (BHMF) was also carried out using sodium borohydride as reducing agent. This latter approach led to prepare rapidly a rather large amount of BHMF. As a result, BHMF derivatization was also investigated. In particular we have focused on BHMF etherification reaction to achieve 2,5-bis(alkoxymethyl) furans (BAMFs) – well-known biofuel candidates. Several catalysts were investigated; (mild) reaction conditions were optimized and thus employed for the preparation of a library of BAMFs (10 compounds). Products isolation and purification were addressed for each BAMFs.[3] Two examples of etherification reactions were also conducted in gram-scale i.e. for the synthesis of 2,5-bis(methoxymethyl)furan and 2,5-bis(isopropoxymethyl) furan.
Ongoing research on BHMF includes studying its reactivity with dialkyl carbonates. The idea is to develop a library of easy accessible bio-based monomers for polycarbonate, polyurethanes as well as potentially interesting intermediates for surfactants and detergents production.[4
Mustard carbonate analogues
Full text linkSulfur and nitrogen (half-)mustard carbonate analogues are a new class of compounds, easily synthesized
by methoxycarbonylation reaction of the parent alcohols with dialkyl carbonates. In this work, their
reactivity as novel, green electrophiles is reported. Reactions have been conducted in autoclave conditions
at high temperature (180 °C), under pressure and in absence of any base, as well as, in neat at atmospheric
pressure, lower temperature (150 °C) and in the presence of a catalytic amount of a base. Several nucleophiles
have been investigated resulting, in some cases, in unexpected compounds, i.e., six-membered heterocycle
piperidine. Reaction mechanism and kinetics have been studied confirming that these compounds retain the
anchimeric effect of their mustard gas analogues, without being toxic. Noteworthy, a symmetrical nitrogen
mustard carbonate has also been employed as reagent in the preparation of a new family of macrocycles i.e.,
azacrowns, before not easily accessible
Sintesi e funzionalizzazione di molecole piattaforma da risorse rinnovabili impiegando carbonati organici
Full text linkIl termine bioraffineria abbraccia tutti i processi basati sulla biomassa che sono studiati come alternativi ai relativi processi/prodotti legati alla raffineria.1 La biomassa è una risorsa molto attraente in quanto fonte di carbonio ampiamente diffusa e a basso costo che include proteine, acidi grassi, lipidi e carboidrati. Tra i componenti della biomassa, i carboidrati ne costituiscono il 75% e rappresentano i composti più promettenti e di maggiore interesse. Le molecole provenienti dalla digestione e frammentazione della biomassa possono essere – a loro volta - funzionalizzate al fine di ottenere una vasta gamma di prodotti e sono per questo definite molecole piattaforma. Nel 2004, il Dipartimento dell'Energia degli Stati Uniti (DOE) ha pubblicato un elenco di molecole piattaforma derivate da risorse rinnovabili considerate di particolare interesse per lo sviluppo della bioraffineria.2 Il D-sorbitolo, l’isosorbitolo e 2,5-idrossimetilfurfurale (HMF) occupano una posizione di rilievo in questa lista dal momento che incorporano tutte le caratteristiche desiderate di una molecola piattaforma. Negli ultimi anni lo studio della reattività del sorbitolo con i dialchil carbonati ha permesso di mettere a punto una strategia sintetica green dell’isosorbide e della sua funzionalizzazione.3 Il dimetil carbonato si è inoltre dimostrato un ottimo solvente per la sintesi dell’HMF. Studi recenti sull’alchilazione del relativo composto ridotto 2,5-diidrossimetilfurano (BHMF) in condizioni blande hanno permesso la sintesi di una libreria di bis(alcossi)furani (Figura 1).4 I derivati dell’isosorbitolo (dimetil isosorbitolo e bis(metossicarbonil)isosorbitolo) e dell’HMF (Bis(idrossimetil)furano, bis(alcossimetil)furano) hanno numerose potenziali applicazioni come solventi green, monomeri per bioplastiche e additivi per carburanti.
Riferimenti
1. R. J. Van Putten, J. C. van der Waal, et al. Chem. Rev. 2013, 113, 1499.
2. T. Werpy, G. Petersen. U.S. Department of Energy, 2004; Vol. I.
3. F. Aricò, A. S. Aldoshin, P. Tundo, ChemSusChem 2017, 10, 53; F. Aricò, P. Tundo, Beilstein J. Org. Chem. 2016, 12, 2256.
4. M. Musolino, J. Andraos, F. Aricò, ChemistrySelect 2018, 3, 2359; M. Musolino, M. J. Ginés-Molina, R. Moreno-Tost, F. Aricò, ACS Sustainable Chem. Eng. 2019, asap artic
Analoghi carbonati delle ipriti
Full text linkI gas mostarda o ipriti, bis(2-cloroetil)solfuro e la bis(2-cloroetil)etilammina, sono tristemente conosciuti per il loro impiego come armi chimiche durante la Prima Guerra Mondiale.1 La tossicità delle ipriti è strettamente correlata alla loro elevata reattività. Infatti, questi composti sono in grado di eliminare lo ione cloruro attraverso una sostituzione nucleofila intramolecolare grazie all’effetto anchimerico dello zolfo o dell’azoto vicinale, generando uno ione episolfonico o aziridinico ciclico che è – a sua volta - estremamente reattivo.2 Nonostante la loro ben nota tossicità, questi composti trovano largo impiego nella preparazione di farmaci, nonché come reagenti per la sintesi di intermedi di reazione.3
Nello studio qui presentato, i dialchil carbonati (DAC)4 – noti reagenti e solventi Green – sono stati fatti reagire con alcoli/dioli precursori dei gas mostarda portando ad una nuova classe di composti: le mostarde carbonate. La reattività degli analoghi carbonati delle ipriti è stata successivamente investigata dimostrando che questi composti preservano l’effetto anchimerico dei gas mostarda, ma non presentano alcuna tossicità, nè pericolo per l’operatore o l’ambiente.5 Le reazioni di alchilazione favorite dall’effetto anchimerico delle mostarde carbonate sono state condotte impiegando diversi nucleofili e operando sia in autoclave ad alta temperatura (180 °C) che in neat a temperature inferiori (150 °C) e a pressione atmosferica. Inoltre, recentemente sono state studiate reazioni di alchilazione in one-pot dove la mostarda carbonata è sintetizzata in situ e reagisce immediatamente con il nucleofilo scelto.
Riferimenti
1. a) J. C. Dacre, M. Goldman, Pharmacol. Rev. 1996, 48, 289–326; b) J. Liu, K. L. Powell, H. D. Thames, M. C. MacLeod, Chem. Res. Toxicol. 2010, 23, 488–496.
2. E. Block in Reactions of Organosulfur Compounds, Academic Press, New York, 1978, pp. 141–145.
3. M. C. S. Barnes, H. J. Dennison, S. S. Flack, J. A. Lumley, P. S. Pang, K. C. Spencer, WO2011/27156, 2011.
4. a) P. Tundo, M. Selva, Acc. Chem. Res. 2002, 35, 9, 706; b) Fabio Arico,̀ A. S. Aldoshin, and P. Tundo, ACS Sustainable Chem. Eng.2016, 4, 2843−2851
5. F. Aricò, M. Chiurato, J. Peltier, P. Tundo. Eur. J. Org. Chem. 2012, 3223–322
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