α-Terpineol is a monoterpene naturally present in essential oils, of high value on the market as it is a compound widely used as a flavoring, aromatic substance in the cosmetics and food industry. This study aims to produce α-terpineol by two different synthetic strategies, using both batch and continuous flow systems, focusing on the optimization of the process, improving the reaction conversion and selectivity. The first strategy adopted was a one-stage hydration reaction of α-pinene by an aqueous solution of chloroacetic acid (molar ratio 1:1 between pinene and the acid) in continuous flow conditions. This reaction was carried out at 80 ºC with a residence time of 15 min, obtaining good values of conversion (72 %) and selectivity (76 %), and productivity of 0.67 Kg.day-1. The second strategy accomplished was a two-step cascade reaction with limonene as starting material, where the first step is a chemo specific double bond addition using trifluoroacetic acid, and the second step is the basic hydrolysis of the ester promoted by a solution of sodium hydroxide (2.25 M) in methanol (1:1). This reaction was adapted to a continuous flow condition, where all steps happen in a residence time of 40 min, at 25 ºC, with no quenching between steps required, giving a conversion of 97 % and selectivity of 81 %, with productivity of 0.12 Kg.day-1.
Keywords: Continuous-flow, α-terpineol, cascade reactions
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When a peer-reviewed version of this preprint is available in the Beilstein Journals, this information will be updated in the information box above. If no peer-reviewed version is available, please cite this preprint using the following information:
de Carvalho, B. L. C.; Aguillon, A. R.; Leão, R. A. C.; de Souza, R. O. M. A. Beilstein Arch. 2020, 202041. doi:10.3762/bxiv.2020.41.v1
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