Studies On Dehydration Of 2-hydroxyethyl Pyridine And Asymmetric Michael Addition Catalyzed By Modified Solid Acid

Solid acid is a green and environmental catalyst. And it is employed for building ecological chemistry instead of environmental polluted catalysts in traditional process. In this paper, the dehydration of 2-hydroxyethyl pyridine to 2-vinyl pyridine was conducted with modified solid acid instead of Br?nsted acid like H2SO4 or strong alkali like Na OH. Meanwhile, the solid acid was modified by asymmetric organocatalysts, which exhibited high enantioselectivity in the asymmetric Michael addition of acetone to ?-nitroolefins. The main details are summarized as follows:1. The dehydration of 2-hydroxyethyl pyridine was carried out with a series of solid acid catalysts and phosphoric acid supported nano-Si O₂?P/SiO₂? exhibited the best catalytic performance. Subsequently, P/SiO₂ catalysts calcined under different temperatures were prepared and characterized by BET, TG, NH3-TPD and Py-IR. It was found that calcination temperature had a significant influence on BET surface area, the pore structure and acidity of the catalysts. When the calcination temperature was 400 °C, the BET surface area and the pore volume reached to the highest. Meanwhile, the amount of Br?nsted acid sites was the biggest, which was beneficial to this dehydration reaction.2. The reaction conditions were optimized under 400P/SiO₂. When this dehydration was carried out at 135 °C for 8 h, 2-hydroxyethyl pyridine could be converted completely and the GC yield of 2-vinyl pyridine was 85.3%. In addition, under the optimized reaction conditions, the catalyst could be recycled three times without obvious deactivation and it exhibited a good recoverability.3.?1R, 2R?-?+?-?1, 2?-Diphenylethanediamine modified sulfuric acid resin was employed for the asymmetric Michael addition of acetone to ?-nitrostyrene. The catalyst exhibited good catalytic activity without any acidic additive. It was found that the moieties of sulfonic acid, primary amine and sulfamide co-existed on the surface of the catalyst according to systematical characterization. This asymmetric Michael addition of acetone was carried out with these three moieties. Under the optimal conditions, the conversion of ?-nitrostyrene was 80.5% and the ee value of the Michael adduct was 84.3%.4. The modified sulfuric acid resin catalyst could be recycled two times with any loss of the enantioselectivity. However, the yield of Michael adduct was decreased. Meanwhile, the asymmetric Michael addition of acetone to ?-nitroolefins was also investigated over this catalyst. The satisfied ?-nitroolefins conversion and the ee value of Michael adducts were obtained?conversion>75.0%, ee value>81.9%?. Obviously, this catalyst exhibited the good generality.