AQUAMEC · Catalytic and mechanistic studies of Organometallic reactions in water: focus on alkylation processes

Catalytic and mechanistic studies of organometallic reactions in water: focus on alkylation processes

The growing interest in organic cyclic carbonates such as glycerol carbonate has been mainly justified for their properties as green polar solvents for use in colours, varnishes, glues, cosmetics and pharmaceuticals, due to their biodegradability, low toxicity and high boiling point. In addition, they are also used in a large variety of different applications such as electrolytes in lithium ion batteries, intermediates for linear dialkyl carbonates synthesis or protecting group in carbohydrate chemistry. Traditionally, the synthetic methods have been focused on the simplest cyclic carbonates which mainly avoid the problems related with the reaction selectivity. Two traditional processes involve reactions of epoxides with carbon dioxide or base-catalised transesterification with other carbonates (dimethyl or diethylcarbonate). Alternatively, it is possible to use a palladium-catalysed direct carbonation of polyols with carbon monoxide. In this project, we have developed an alternative Pd-catalysed transesterification of diallyl carbonate with polyols via a reversible decarboxylation-carboxylation process with CO2. Over the past decades, the advances that have been made in selective and efficient organic reactions have truly revolutionised the field of synthesis. In this context, we have reported on an investigation into the base-catalysed transesterification using tetraols, pentaols and hexaols with different stereochemistry. Notably, most of the tested polyols afforded cyclic mono carbonates almost quantitatively with excellent selectivity at room temperature and catalytic amount of base. Additionally, we study a competitive and reversible epimerisation of polyols with a special emphasis in the inter-conversion of erythritol to threitol which encourages us to undertake the study of its inner workings in more detail. Finally, we synthesised a very reactive transesterification reagent ('MAC') derivated from mannitol that is of great potential utility in synthesis. Initial studies have shown that 'MAC' is substantially more reactive than other standard carbonylation reagents and is possible to carry out enantioselective reaction without chiral ligands or organometallic catalysts. In conclusion, the initial project of allylation reaction in aqueous medium with diallyl carbonate moved on to other interesting topics, such as transesterification or epimerisation reaction of polyols and synthesis of cyclic carbonates. In addition to scientific work, the fellow made many new scientific contacts in Bristol and in the United Kingdom, with which he will build foundations for promising collaboration in the longer term development of his career. Moreover, he developed his collaborative abilities by contributing to the teaching of workshops and co-supervising master and Doctor of Philosophy (PhD) students. The socio-economic impact of the project is found in two aspects: the training of the co-worker (Dr Gordillo) in the area of physical organic chemistry - this aiding his mobility and utility in the European Union scientific research base - and in the potential for utility of the transesterification process in industrial applications; the latter aspect is being explored.

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