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Capillary monolithic column as a microreactor for asymmetric Henry reaction in flow
Autoři: Svoboda Jan | Nováková Gabriela | Drabina Pavel | Sedlák Miloš
Rok: 2018
Druh publikace: ostatní - přednáška nebo poster
Strana od-do: nestránkováno
Tituly:
Jazyk Název Abstrakt Klíčová slova
eng Capillary monolithic column as a microreactor for asymmetric Henry reaction in flow We have designed, characterized and optimized the new microreactor – capillary monolithic column for asymmetric Henry reaction in the continuous flow conditions. This work based on our previous research and intention to extend the obtained results from the heterogeneously catalysed asymmetric Henry reaction in the batch system [1]. The base of the catalytic site is the chiral ligand coordinated by copper acetate, which is chemically bonded to monolith from polystyrene crosslinked by divinylbenzene. The catalytically active site in the monolith must be accessible for reactants. When the so-called copolymeration strategy of synthesis was used, the consecutive complexation of the monolith by copper acetate was not possible and therefore the catalytically active sites were not created. For this reason, the so-called post-modifying strategy of synthesis was used. First, a monolith containing the active chloromethylated sites and a porogen was prepared by thermally initialized radical polymeration. Next, the porogen was eluted and the monolith was modified by the reaction solution of the ligand and DBU in dimethylsulfoxide. The last modification step was the complexation reaction with methanolic solution of copper acetate. All washing and reaction solutions were dosed from the Hamilton syringe pump directly to the capillary. With the catalytically active column in hand, the reaction conditions were optimized and the asymmetric Henry reactions of series of aldehydes with nitromethane were studied. It was found that the monolith prepared is able to catalysed asymmetric Henry reaction in flow with good conversion and enantioselectivity up to 90 % ee. The stability of the reactor under continuous flow was verified by constant conversion and enantioselectivity over time. Henry reaction; assymetric; Capillary monolithic column