Esteban Noelia, Ferrer María L, Ania Conchi O, de la Campa José G, Lozano Ángel E, Álvarez Cristina, Miguel Jesús A
IU CINQUIMA, Universidad de Valladolid, Paseo Belén 5, E-47011 Valladolid, Spain.
Materials Science Factory, Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Campus de Cantoblanco, 28049 Madrid, Spain.
ACS Appl Mater Interfaces. 2020 Dec 23;12(51):56974-56986. doi: 10.1021/acsami.0c16184. Epub 2020 Dec 11.
A new generation of confined palladium(II) catalysts covalently attached inside of porous organic polymers (POPs) has been attained. The synthetic approach employed was straightforward, and there was no prerequisite for making any modification of the precursor polymer. First, POP-based catalytic supports were obtained by reacting one symmetric trifunctional aromatic monomer (1,3,5-triphenylbenzene) with two ketones having electron-withdrawing groups (4,5-diazafluoren-9-one, DAFO, and isatin) in superacidic media. The homopolymers and copolymers were made using stoichiometric ratios between the functional groups, and they were obtained with quantitative yields after the optimization of reaction conditions. Moreover, the number of chelating groups (bipyridine moieties) available to bind Pd(II) ions to the catalyst supports was modified using different DAFO/isatin ratios. The resulting amorphous polymers and copolymers showed high thermal stability, above 500 °C, and moderate-high specific surface areas (from 760 to 935 m g), with high microporosity contribution (from 64 to 77%). Next, POP-supported Pd(II) catalysts were obtained by simple immersion of the catalyst supports in a palladium(II) acetate solution, observing that the metal content was similar to that theoretically expected according to the amount of bipyridine groups present. The catalytic activity of these heterogeneous catalysts was explored for the synthesis of biphenyl and terphenyl compounds, via the Suzuki-Miyaura cross-coupling reaction using a green solvent (ethanol/water), low palladium loads, and aerobic conditions. The findings showed excellent catalytic activity with quantitative product yields. Additionally, the recyclability of the catalysts, by simply washing it with ethanol, was excellent, with a sp-sp coupling yield higher than 95% after five cycles of use. Finally, the feasibility of these catalysts to be employed in tangible organic reactions was assessed. Thus, the synthesis of a bulky compound, 4,4'-dimethoxy-5'--butyl--terphenylene, which is a precursor of a thermal rearrangement monomer, was scaled-up to 2 g, with high conversion and 96% yield of the pure product.
已制备出新一代共价连接在多孔有机聚合物（POPs）内部的受限钯（II）催化剂。所采用的合成方法简单直接，无需对前驱体聚合物进行任何改性。首先，通过使一种对称三官能芳族单体（1,3,5-三苯基苯）与两种具有吸电子基团的酮（4,5-二氮杂芴-9-酮，DAFO，和异吲哚酮）在超酸性介质中反应，获得基于POP的催化载体。使用官能团之间的化学计量比制备均聚物和共聚物，并在优化反应条件后以定量产率获得。此外，使用不同的DAFO/异吲哚酮比例改变可用于将钯（II）离子结合到催化剂载体上的螯合基团（联吡啶部分）的数量。所得的无定形聚合物和共聚物表现出高于500°C的高热稳定性以及中高比表面积（760至935 m²/g），具有高微孔率贡献（64至77%）。接下来，通过将催化剂载体简单浸入乙酸钯溶液中获得POP负载的钯（II）催化剂，观察到金属含量与根据存在的联吡啶基团数量理论预期的含量相似。通过使用绿色溶剂（乙醇/水）、低钯负载量和有氧条件的铃木-宫浦交叉偶联反应，探索了这些多相催化剂用于合成联苯和三联苯化合物的催化活性。结果表明其具有优异的催化活性，产物产率达到定量。此外，通过简单用乙醇洗涤，催化剂的可回收性极佳，在使用五个循环后sp-sp偶联产率高于95%达到96%。最后，评估了这些催化剂用于实际有机反应的可行性。因此，将一种大体积化合物4,4'-二甲氧基-5'-丁基-三联苯（一种热重排单体的前体）的合成放大至2 g，纯产物具有高转化率和96%的产率。
