半乳糖氧化酶模型化合物对乙苯选择性氧化制备苯乙酮的催化性能及机理  

Catalytic performance and mechanisms of GOase model compound on selective oxidation of ethylbenzene to acetophenone

作　　者：刘晓辉 黄佳莹 薛灿 周贤太 LIU Xiaohui;HUANG Jiaying;XUE Can;ZHOU Xiantai(School of Chemical Engineering and Technology,Sun Yat-sen University,Zhuhai 519082,Guangdong,China;Huizhou Research Institute,Sun Yat-sen University,Huizhou 516081,Guangdong,China)

机构地区：[1]中山大学化学工程与技术学院,广东珠海519082 [2]中山大学惠州研究院,广东惠州516081

出　　处：《精细化工》2024年第11期2538-2545,共8页Fine Chemicals

基　　金：国家自然科学基金项目(22278451、21938001);广东省基础与应用基础研究基金项目(2023A1515111144、2022B1515120057、2019A1515110979)。

摘　　要：温和条件下实现C—H键的选择性氧化在精细化学品的生产中发挥着重要的作用。受半乳糖氧化酶的活性中心结构和催化循环启发,合成了模型化合物N,N'-双(2-羟基-3,5-二叔丁基苯基)-2,2'-二氨基联萘合铜〔CuL,L=N,N'-双(2-羟基-3,5-二叔丁基苯基)-2,2'-二氨基联萘〕。以CuL为催化剂、N-羟基邻苯二甲酰亚胺(NHPI)为助催化剂,考察了乙苯选择性氧化制备苯乙酮的催化性能,并探讨了可能的反应机理。结果表明,在温和条件下(初始O_(2)1.0 MPa、75℃、反应时间8 h),乙苯转化率可达99%,苯乙酮选择性可达99%。CuL与NHPI形成了活性中间体,通过电子转移,高效促进了NHPI生成邻苯二甲酰亚胺-N-氧基(PINO)自由基,从而实现了乙苯C—H键的活化。由动力学同位素效应实验推测,NHPI的活化可能为决速步骤(NHPI和氘代NHPI的反应速率比值约为3.4)。电子顺磁共振和高分辨质谱结果表明,反应过程中存在烷基自由基、过氧自由基和羟基自由基。Selective oxidation of C—H bonds under mild conditions plays an important role in the production of fine chemicals.Inspired by the active center structure and catalytic cycle of galactose oxidase,model compound CuL,with L referring to the ligand of N,N'-bis(2-hydroxy-3,5-di-tert-butylphenyl)-2,2'-diaminonaphthyl,was synthesized,and evaluated for its catalytic performance as well as mechanism on selective oxidation of ethylbenzene to acetophenone using N-hydroxyphthalimide(NHPI)as cocatalyst.The results showed that under mild conditions(initial O_(2) pressure 1.0 MPa,75℃,reaction time 8 h),the conversion rate of ethylbenzene was up to 99%,while the selectivity of acetophenone was also up to 99%.The reaction mechanism could be attributed to the active intermediates formed by CuL and NHPI,which efficiently promoted NHPI generating phthalimide N-oxyl(PINO)radicals through electron transfer and thus achieved the C—H bond activation of ethylbenzene.Data from kinetic isotope effect experiments suggested that the activation of NHPI might be a rate-determining step(the ratio of reaction rates between NHPI and deuterated NHPI was about 3.4).The results of electron paramagnetic resonance and high-resolution mass spectrometry revealed that there were alkyl radicals,peroxy radicals and hydroxyl radicals generated during the reaction.

关 键 词：半乳糖氧化酶 仿生催化 乙苯 自由基 氧化 精细化工中间体 

分 类 号：TQ244.2[化学工程—有机化工]