Carbonate based ionic liquids and beyond

Ionic liquids appear almost like a different state of matter. Just like mercury, that I enjoyed playing with as a child after bursting thermometers. A liquid metal, and a liquid salt at room temperature are awe-inspiring, as their physical state is counterintuitive. We struggle to accept that a metal may not be hard, and that a salt may be non-crystalline, let alone liquid. Thus, for sheer curiosity, we started synthesising ammonium and phosphonium ionic liquids. The first hurdle was to make them efficiently, colourless and pure. And this was achieved by using dimethylcarbonate (non-toxic) instead of alkyl halides as quaternarisation reagent. These syntheses were, efficient (100% atom economic), tuneable, halide-free, and produced only CO2 and methanol as by-products.1 But, ionic liquids are not just pretty. So what can we do with them? Use them as green solvents? Sometimes yes, but often too costly, and not always an elegant or green application. Unless we can design multiphase solvent systems with other advantages.2-3 It’s might also interesting to take advantage of the chemical properties of their ions,4 or to use them as catalysts,5-6 including for the upgrade of biogenic chemicals.7 The next question might be on how these materials work, e.g. as catalysts,8 and how can these properties be monitored.9 Or whether they can be used to make new devices, e.g. based on their luminescence.10 And why not try to make old compounds, e.g. choline, by these methods? We will discuss this “genealogy” of applications and of examples, applied to a family of carbonate based ionic liquids. 1. Fabris, M.; Lucchini, V.; Noè, M.; Perosa, A.; Selva, M., Chem. Eur. J. 2009, 15 (45), 12273-12282. 2. Tundo, P.; Perosa, A., Chem. Soc. Rev. 2007, 36 (3), 532-550. 3. Gottardo`, M.`; Selva`, M.`; Perosa`, A. work in progress 4. Noè, M.; Perosa, A.; Selva, M.; Zambelli, L., Green Chem. 2010, 12 (9), 1654-1660. 5. Fabris, M.; Noe, M.; Perosa, A.; Selva, M.; Ballini, R., J. Org. Chem. 2012, 77 (4), 1805-1811. 6. Selva, M.; Noe, M.; Perosa, A.; Gottardo, M., Org. Biomol. Chem. 2012, 10 (32), 6569-6578. 7. Stanley`, J.`; Caretto`, A.`; Perosa`, A. work in progress 8. Lucchini, V.; Noè, M.; Selva, M.; Fabris, M.; Perosa, A., Chem. Commun. 2012, 48 (42), 5178-5180. 9. Lucchini, V.; Fabris, M.; Noe, M.; Perosa, A.; Selva, M., Int. J. Chem. Kinet. 2011, 43 (3), 154-160. 10. Fiorani`, G.; Selva, M.; Perosa`, A.`; Malba, C.; work in progress

Concatenated batch and continuous flow procedures for the upgrading of glycerol-derived aminodiols via N-acetylation and acetalization reactions

An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80-90 \ub0C, both substrates were quantitatively converted into the corresponding amides through a catalystfree N-acetylation reaction mediated by an innocuous enol ester as isopropenyl acetate (iPAc). Thereafter, at 30-100 \ub0C and 1-10 atm, the amide derivatives underwent a selective CF-acetalisation in the presence of acetone and a solid acid catalyst, to afford the double-functionalized (amideacetal) products

Ionic Liquids Made with Dimethylcarbonate: Solvents as well as Boosted Basic Catalysts for the Michael Reaction

Abstract: This article describes 1) a methodology for the green synthesis of a class of methylammonium and methylphosphonium ionic liquids (ILs), 2) how to tune their acid–base properties by anion exchange, 3) complete neat-phase NMR spectroscopic characterisation of these materials and 4) their application as active organocatalysts for base-promoted carbon– carbon bond-forming reactions. Methylation of tertiary amines or phosphines with dimethyl carbonate leads to the formation of the halogen-free methyl-onium methyl carbonate salts, and these can be easily anion-exchanged to yield a range of derivatives with different melting points, solubility, acid–base properties, stability and viscosity. Treatment with water, in particular, yields bicarbonate-exchanged liquid onium salts. These proved strongly basic, enough to efficiently catalyse the Michael reaction; experiments suggest that in these systems the bicarbonate basicity is boosted by two orders of magnitude with respect to inorganic bicarbonate salts. These basic ionic liquids used in catalytic amounts are better even than traditional strong organic bases. The present work also introduces neat NMR spectroscopy of the ionic liquids as a probe for solute– solvent interactions as well as a tool for characterisation. Our studies show that high catalytic efficacy of functional ionic liquids can be achieved by integrating their green synthesis, along with a fine-tuning of their structure. Demonstrating that ionic liquid solvents can be made by a truly green procedure, and that their properties and reactivity can be tailored to the point of bridging the gap between their use as solvents and as catalysts. Keywords: dimethyl carbonate · green chemistry · ionic liquids · Michael addition · NMR spectroscop

Concatenated batch and continuous flow procedures for the upgrading of glycerol-derived aminodiols via N-acetylation and acetalization reactions

An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80-90 °C, both substrates were quantitatively converted into the corresponding amides through a catalystfree N-acetylation reaction mediated by an innocuous enol ester as isopropenyl acetate (iPAc). Thereafter, at 30-100 °C and 1-10 atm, the amide derivatives underwent a selective CF-acetalisation in the presence of acetone and a solid acid catalyst, to afford the double-functionalized (amideacetal) products

CO2-assisted hydrolytic hydrogenation of cellulose and cellulose-based waste into sorbitol over commercial Ru/C

A single-step protocol was developed for the hydrolytic hydrogenation of microcrystalline cellulose into sorbitol over commercial carbon-supported Ru, in the presence of gaseous CO2 as an acid source and molecular hydrogen as a reductant. Under these conditions, cellulose was first hydrolysed to glucose by reversibly formed carbonic acid in water and then instantaneously hydrogenated on Ru/C. By tuning the reaction parameters, such as temperature, time and the relative pressure of CO2 and hydrogen gas, cellulose was fully converted at 220 & DEG;C in 18 h under 30 and 40 bar of H-2 and CO2, respectively, with a sorbitol yield of 81%. Blank experiments revealed that without a catalyst and hydrogen, the reaction exhibited <5% conversion and glucose was the only detected product when the reaction was performed under CO2 pressure. XRD measurements on CO2-treated cellulose surprisingly revealed no noticeable changes in the crystallinity index (<10% with respect to microcrystalline cellulose), suggesting that hydrolytic hydrogenation took place on crystalline, not amorphous, cellulose. Furthermore, not only several cellulosic feedstocks, including filter paper, cotton wool, and cotton fiber, but also typical cellulose-based wastes such as a cardboard pizza box were also tested and under the optimized conditions sorbitol was obtained with yields ranging from 56% up to 72% in all cases. No less significant was the Ru/C catalyst stability, which could be recycled at least six times without any noticeable activity loss

Selective hydrogenolysis of glycerol with Raney nickel

Glycerol, a cheap renewable feedstock, was converted selectively to 1,2-propanediol by heating under low hydrogen pressure (10 bar), in the presence of Raney nickel. No solvents or additives were required, and the product could be distilled out of the reaction mixture. Addition of a phosphonium salt, a liquid at the reaction temperature, improved the selectivity and rate to a small extent but did not facilitate the separation of the final reaction mixture