28165-49-3Relevant articles and documents
Hollow, mesoporous, eutectic Zn1?xMgxO nano-spheres as solid acid-base catalysts for the highly regio-selectiveO-methylation of 1,2-diphenols
Liu, Jie,Ma, Xuebing,Wang, Xuri,Xie, Guangxin,Yin, Zuyong,Zhang, Jianing
, p. 7454 - 7466 (2021/11/23)
The highly regio-selectiveO-methylation of catechol with dimethyl carbonate (DMC), catalyzed by a solid acid-base catalyst, is an environmentally friendly chemical process for industrial production of guaiacol. However, a guaiacol yield below 84% and high reaction temperature above 280 °C limit its industrial application. Here, hollow, mesoporous Zn1?xMgxO nano-spheres with a eutectic structure, denoted as Zn1?xMgxO HMNSs (x= 0.012-0.089), are facilely fabricatedviathe calcination of Mg2+/Zn2+ion-adsorbing carbon spheres at 500 °C in air. In theO-methylation of catechol with DMC at 180 °C, Zn1?xMgxO HMNSs (x= 0.052) afford guaiacol in 95.5% yield with a complete catechol conversion. Furthermore, 89.0-95.3% mono-ether yields with high 1,2-diphenol conversions (94.5-100%) are also obtained for the other 1,2-diphenols bearing -CH3and -Br groups. Moreover, a plausible mechanism for highly selectiveO-methylation of catechol with DMC is proposed, in which the single-site activation and double-site activation of phenolic hydroxyls by the basic oxygen of Mg-O afford guaiacol and veratrole, respectively.
Investigating the microwave-accelerated Claisen rearrangement of allyl aryl ethers: Scope of the catalysts, solvents, temperatures, and substrates
Hui, Zi,Jiang, Songwei,Qi, Xiang,Ye, Xiang-Yang,Xie, Tian
supporting information, (2020/05/18)
The microwave-accelerated Claisen rearrangement of allyl aryl ethers was investigated, in order to gain insight into the scope of the catalysts, solvents, temperatures, and substrates. Among the catalysts examined, phosphomolybdic acid (PMA) was found to greatly accelerate the reaction in NMP, at temperatures ranging from 220 to 300 °C. This method was found to be useful for preparing several intermediates previously reported in the literature using precious metal catalysts such as Au(I), Ag(I), and Pt(II). Additionally, substrates bearing bromo and nitro groups on the aryl portion required careful tailoring of the reaction conditions to avoid complex product profiles.
Mild and Regioselective Bromination of Phenols with TMSBr
Ma, Xiantao,Yu, Jing,Jiang, Mengyuan,Wang, Mengyu,Tang, Lin,Wei, Mengmeng,Zhou, Qiuju
supporting information, p. 4593 - 4596 (2019/07/05)
In this work, an unexpected promoting effect of by-product thioether was observed, leading to a mild and regioselective bromination of phenols with TMSBr. This method can tolerate a series of functional groups such as the reactive methoxyl, amide, fluoro, chloro, bromo, aldehyde, ketone and ester groups, and has the potential to recycle the by-product thioether and isolate the desired product under column chromatography-free conditions. Mechanism studies revealed that O–H···S hydrogen bond may be formed between phenol and by-product thioether. Possibly owing to the steric hindrance effect from by-product thioether, the electrophilic bromination at para-position of phenols is much favorable.
