The Synthesis of Bio-derived, Novel Cyclic Organic Carbonates

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The synthesis of glycerol carbonate via several methods has been reviewed extensively, 1-3 which confirms that it is a molecule of high interest and potential value. A large factor in the value of glycerol carbonate, is that it is a viable route to upgrade otherwise waste glycerol from biodiesel production. The interest, value, and applications which have already been demonstrated for glycerol carbonate is the driving factor in the interest in the synthesis of cyclic carbonates from other sugar alcohols in this project. The synthesis and applications of novel cyclic carbonates from other polyols, which can be readily derived from sugar-feedstocks by a simple hydrogenation of the corresponding sugar will be studied. The starting point for the project is the unpublished work from within the group which has shown that cyclic carbonates can be synthesised by reactions of sugar alcohols with urea, dimethyl carbonate or carbonyl diimidazole, in chemical or enzyme catalysed routes or without catalysis. Each of these reactions has its benefits and its drawbacks, however, so comparing between the reaction types will allow for the optimum method to be determined. The aim of the work is to design reaction methods which will allow for selective synthesis of the cyclic carbonates, by all the above routes. As these are novel compounds, with no standards available, the first step will to be design a reaction and purification to give these carbonate standards, which will need to be fully characterised (NMR, CHN, Mass spec, FTIR). These standards can then be used for identification of reaction products from synthesis where multiple products are possible (e.g. reactions with Urea which can have lower selectivity), and for exploring potential applications such as polymerisation reactions. Once a reliable route to standards has been identified, reaction methods using more sustainable reagents will be developed. Previous work has shown that these reactions can have reduced selectivity, so it will be important to design the reactions carefully, chose catalysts, conditions, and reagent ratios to maximise the yield of the desired carbonates. The effect of temperature and different catalysts/enzymes will be explored. There is also the possibility, to carry out the reaction under reduced pressure, and distil products in-situ, which would be excellent for future industrial synthesis. The routes can then be compared in terms of yield, selectivity, efficiency and 'green' credentials to determine the optimum route to the cyclic carbonates. References:1. Christy, S.; Noschese, A.; Lomeli-Rodriguez, M.; Greeves, N.; Lopez-Sanchez, J. A., Recent progress in the synthesis and applications of glycerol carbonate. Current Opinion in Green and Sustainable Chemistry 2018, 14, 99-107.2. Sonnati, M. O.; Amigoni, S.; Taffin de Givenchy, E. P.; Darmanin, T.; Choulet, O.; Guittard, F., Glycerol carbonate as a versatile building block for tomorrow: synthesis, reactivity, properties and applications. Green Chemistry 2013, 15 (2), 283-306.3. Ochoa-Gómez, J. R.; Gómez-Jiménez-Aberasturi, O.; Ramirez-López, C.; Belsué, M., A Brief Review on Industrial Alternatives for the Manufacturing of Glycerol Carbonate, a Green Chemical. Organic Process Research & Development 2012, 16 (3), 389-399.