Surface-driven imidazolium-coated periodic mesoporous organosilicas for selective synthesis of electron-deficient 2-arylbenzo[d]oxazoles

• Published in: Microporous and mesoporous materials 2020-03, Vol.294, p.109922, Article 109922
• Main Authors: Cui, He-Zhen, Zhou, Quan, Hong, Xi, Huang, Shuang, Zhan, Bing, Hou, Xiu-Feng
• Format: Article
• Language: English
• Subjects: Hydrophobicity modulation; Mesoporous organosilicas; Performance reversal; Selective adsorption
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2019.109922

Selective synthesis driven by appropriate support properties of heterogeneous catalysts is promising, but long-term process to explore. In this work, we prepared and confirmed series of hydrophobic ethyl bridges modulated periodic mesoporous organosilica fixed with 1-methyl-3-(3-(trimethoxysilyl)propyl)-1H-imidazole-3-iumiodide (MBIm-PMO-x). The contents of hydrophobic ethyl bridges (x) were 0, 5, 15, 25, 35 mol%. These materials were applied for synthesizing heterocyclic compound 2-arylbenzoxazoles with arylaldehydes and 2-aminophenol. Among them, MBIm-PMO-15, hydrophobic ethyl bridge was 15 mol%, dramatically enhanced the yields of synthesizing electron-deficient 2-arylbenzoxazoles. For substrates with different electronic properties, we found MBIm-PMO-15 exhibited the reversed catalytic activity in relation to corresponding homogeneous MBIm. Further research, FT-IR adsorption and UV–vis detection tests demonstrated this kind heterogeneous catalyst surface prefers adsorbing electron-deficient intermediates Schiff base to electron-rich ones. It is the specific adsorption motivate MBIm-PMO-15 highly selectivity towards electron-deficient 2-arylbenzoxazoles. In a broader vision, surface driven selective adsorption of heterogeneous catalyst for substrate could act as an alternative strategy to get special target products. [Display omitted] •MBIm-PMO-15 with appropriate wettability modulated by hydrophobic ethyl bridges was obtained.•MBIm-PMO-15 possess superior performance and selectivity for synthesis of electron-deficient 2-arylbenzoxazoles.•The catalytic performance of MBIm-PMO-15 was polar opposite compared to homogeneous MBIm.•The highly selectivity was driven by specific electron-deficient substrate-catalyst adsorption.