Accumulation of Active Species in Silica Mesopore: Effect of the Pore Size and Free Base Additives on Pd‐catalyzed Allylation using Allylic Alcohol
Accumulation of Active Species in Silica Mesopore: Effect of the Pore Size and Free Base Additives on Pd‐catalyzed Allylation using Allylic Alcohol
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DOI：
10.1002/cctc.202000266
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发表时间：
2020-05
期刊：
影响因子：
4.5
通讯作者：
Ken Motokura;Sae Kawashima;Masayuki Nambo;Yuichi Manaka;W. Chun
中科院分区：
文献类型：
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作者：
Ken Motokura;Sae Kawashima;Masayuki Nambo;Yuichi Manaka;W. Chun
采用不同类型的多孔二氧化硅载体（孔径：16-31 Å）制备介孔二氧化硅负载Pd配合物。考察了孔径和碱添加剂性质对烯丙基化反应的影响。Pd催化的亲核试剂与特定碱添加剂（如1,8 -重氮双环[5.4.0]undec - 7 - ene (DBU)）的烯丙基化活性受到介孔大小的强烈影响。孔径为23 Å时，烯丙基化性能最佳。另一方面，具有较小/较大分子尺寸和/或高亲核性的碱，如K2CO3和1,4‐重氮双环[2.2.2]辛烷（DABCO），似乎对催化没有明显的孔效应。使用这些碱基后，催化烯丙化反应的性能明显降低。动力学、光谱和控制实验表明，适当孔径的介孔中Pd和DBU的有效积累提高了它们的频率因子。
A mesoporous silica‐supported Pd complex was prepared using various types of porous silica supports (pore size: 16–31 Å). The effects of the pore size and base additive properties on the catalytic allylation were investigated. The activity of the Pd‐catalyzed allylation of nucleophiles with specific base additives, such as 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), is strongly affected by the mesopore size. The best allylation performance is obtained with a pore size of 23 Å. On the other hand, bases with smaller/larger molecular size and/or high nucleophilicity, such as K2CO3 and 1,4‐diazabicyclo[2.2.2]octane (DABCO), do not seem to show clear pore effect on the catalysis. The performance of the catalytic allylation significantly decreases by using such bases. Kinetic, spectroscopic, and control experiments reveal that the effective accumulation of Pd species and DBU in mesopores with appropriate pore sizes enhances their frequency factors.