Tandem reactions for the synthesis of fatty acids derivatives

Resumen del póster presentado al International Symposium on Green Chemistry (ISGC), celebrado en La Rochelle (Francia) del 16 al 19 de mayo de 2017.Nowadays, there is a trend to reduce dependence on fossil fuels in the production of chemicals, increasing the use of renewable raw materials in biorefinery processes that support the development of a more sustainable chemistry. In order to achieve this goal, catalysis has been and will be of great importance because biomass has a greater chemical diversity than oil. For this reason, the catalytic conversion of biomass and derivatives to chemicals of interest has been a subject of intense research efforts during the past decade. Fatty acids and their derivatives, as part of the biomass, constitute the starting materials of the classical oleochemical industry. In this industry, around 90% of the processes involve the transformation of the carboxylic group. However, the transformation of the hydrocarbon chain of fatty acids allowing the obtaining of products with high added value it is also interesting, and a lot of reactions have been described in the literature for the modification of C=C double bonds of unsaturated fatty acids. In particular, oxidation reactions on the double bond can lead to a variety of interesting compounds. The epoxidation reaction is an important example of oxidation of the double bonds of fatty acids. Another example is the direct oxidation of the double bond with oxygen (Wacker oxidation) to obtain fatty ketoesters. The latter compounds can alternatively be obtained by a catalytic rearrangement of the corresponding epoxide. The possibility of carrying out processes with several catalytic steps in the same reactor or in other words, using a tandem process, would be an attractive and efficient approach with operational and economic advantages. The use of tandem reactions avoids intermediate purifications which increase the sustainability of the process. An example of these methodology applied to the transformations of double bonds of unsaturated fatty acids is reported in this work. Methyl oxostearates are obtained following a tandem route that involves the epoxidation of methyl oleate and the subsequent rearrangement of the obtained epoxide using heterogeneous catalysts, all in one-pot. Reaction conditions and recoverability of catalysts have been studied and optimized. In this tandem process, the epoxidation of methyl oleate was carried out with a supported titanium catalyst and tert-butyl hydroperoxide as an oxidant. Then, the epoxide rearrangement was promoted by different acid catalysts with excellent results. More than 95% total yield was obtained as result of the combination of both reactions in a tandem procedure, without intermediate purification. In addition, the reusability of both catalysts was tested with good results, improving the productivity of the catalysts and the sustainability of the method.Peer reviewe