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首页> 外文期刊>Catalysis science & technology >Cycloaddition of CO2 and epoxides catalyzed by imidazolium bromides under mild conditions: influence of the cation on catalyst activity
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Cycloaddition of CO2 and epoxides catalyzed by imidazolium bromides under mild conditions: influence of the cation on catalyst activity

机译：在轻度条件下，由咪唑溴化物催化的二氧化碳和环氧化物的环加成：阳离子对催化剂活性的影响

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摘要

The synthesis and characterization of a library of imidazolium-based compounds of the type [R~1R~2R~3im]Br (R~1= H, CH3, benzyl (Bz), l-(2,3,4.5,6-pentafluoro)benzyl (Bz~(F5)); R~1 = H, CH3, C2H5; R~3 = n-butyl, n-octyl) are reported. All compounds were characterized by means of ~1H and ~(13)C NMR spectroscopy, elemental analysis and single crystal X-ray diffraction in the case of l-Bz~(F5)-3-n-octylimidazolium bromide and examined as catalysts for the cycloaddition of carbon dioxide and propylene oxide (PO) to yield propylene carbonate (PC). The catalyst screening shows the influence of different substituents (steric and ion pairing effects) on the catalytic activity. It is shown that the most active catalyst, l-Bz~(F5)-3-n-octylimidazolium bromide (10), gives very good conversions and carbonate yields at 70 °C and below 5 bar CO2 pressure, which is the lowest temperature for the synthesis of PC from PO and CO2 using metal-free catalysts. Catalyst 10 can be recycled and reused at least 10 times without loss of yield and activity.
机译：[r〜1r〜2r〜3im] br（r〜1 = h，ch3，benzyl（bz），l-（2,3.4.5,6--报道了pentafluoro）苄基（bz〜（f5））; r〜1 = h，ch3，c2h5; r〜3 = n丁基，n-辛基）。在L-Bz〜（F5）-3-N-N- Octylimidazolium溴化物的情况下，通过〜1H和〜（13）C NMR光谱，元素分析和单晶体X射线衍射均表征所有化合物的表征二氧化碳和氧化丙烷（PO）的环加成可产生碳酸丙二醇（PC）。催化剂筛选显示了不同取代基（空间和离子配对效应）对催化活性的影响。结果表明，最活跃的催化剂l-bz〜（F5）-3-n- occtylimidazolium溴化物（10）可在70°C和低于5 bar CO2压力下提供非常好的转化率，碳酸盐的产量为最低温度，这是最低温度用于使用无金属催化剂从PO和CO2合成PC。催化剂10可以回收并重复使用至少10次，而不会损失产量和活性。

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