A solvent-free organocatalyzed process for the transesterification of dimethyl carbonate (DMC) with 1,2-diols under scalable continuous flow conditions is presented. Process parameters, such as temperature, residence time, DMC/glycerol molar ratio and catalyst loading are optimized for the carbonation of bio-based glycerol using 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) as a model organocatalyst. The catalytic performance of DBU is next compared with other homogeneous organic superbases including the proton sponge, Verkade's base, guanidines and phosphazenes. 2-tert-Butyl-1,1,3,3-tetramethylguanidine (Barton's base) stands as the most efficient organocatalyst, providing glycerol carbonate at 87% selectivity and 94% conversion within 2 minutes of residence time at 1 mol% loading. Representative examples of polystyrene-supported (PS) organic superbases of the amidine, guanidine and phosphazene-types are also considered as alternative heterogeneous catalysts. PS superbases typically enable up to 80 h of continuous operation with minor deactivation at elevated flow rates. The methodology is amenable to a library of other 1,2-diols, including biomass-derived substrates. Depending on the unique structural features of both substrates and products, either on-line IR or on-line NMR analytical procedures are implemented for real-time qualitative reaction monitoring. A final demonstrator showcases the transposition of the glycerol carbonation to a pilot-scale continuous flow reactor, affording the target cyclic carbonate with a 68.3 mol per day productivity (∼8 kg per day).

中文翻译：

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可扩展的连续流动条件下无溶剂有机催化制备环状有机碳酸酯†

提出了一种无溶剂的有机催化方法，用于在可扩展的连续流动条件下使碳酸二甲酯（DMC）与1,2-二醇进行酯交换反应。使用1,8-二氮杂双环（5.4.0）十一碳-7-烯（DBU）作为模型，针对生物基甘油的碳酸化优化了工艺参数，例如温度，停留时间，DMC /甘油摩尔比和催化剂负载量有机催化剂。接下来将DBU的催化性能与其他均质有机超强碱（包括质子海绵，Verkade碱，胍和磷腈）进行比较。2叔-丁基1,1,1,3,3-四甲基胍（巴顿碱）是最有效的有机催化剂，在1 mol％负载的停留时间内2分钟内，碳酸酯甘油酯的选择性为87％，转化率为94％。considered，胍和磷腈型的聚苯乙烯负载的（PS）有机超强碱的代表性实例也被认为是替代的非均相催化剂。PS超级碱通常可实现长达80小时的连续运行，并在较高的流速下略有失活。该方法适用于其他1,2-二醇库，包括生物质衍生的底物。根据底物和产品的独特结构特征，可以执行在线IR或在线NMR分析程序来进行实时定性反应监测。