标题:Theoretical investigation on the chiral diamine-catalyzed epoxidation of cyclic enones: Mechanism and effects of cocatalyst
作者:Lv, P.-L.;Zhu, R.-X.;Zhang, D.-J.;Duan, C.-G.;Liu, C.-B.
作者机构:[Lv, P.-L] Key Lab of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan 250100, China;[ Zhu, R.-X] Key Lab of Colloid 更多
通讯作者:Zhu, RX
通讯作者地址:[Zhu, RX]Shandong Univ, Key Lab Colloid & Interface Chem, Minist Educ, Sch Chem & Chem Engn, Jinan 250100, Peoples R China.
来源:The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory
出版年:2012
卷:116
期:4
页码:1251-1260
DOI:10.1021/jp207914h
摘要:The asymmetric epoxidation of 2-cyclohexen-1-one with aqueous H _2O _2 as oxidant, 1,2-diaminocyclohexane as catalyst, and a Br?nsted acid trifluoroacetic acid (TFA) as cocatalyst has been studied by performing density functional theory calculations. It is confirmed that the catalyzed epoxidation proceeds via sequential nucleophilic addition and ring-closure processes involving a ketiminium intermediate. Four possible pathways associated with two Z isomers and two E isomers of ketiminium have been explored in detail. Our calculation indicates that these four pathways have high barriers and a small energy gap between two more favorable R and S pathways. We have analyzed the effects of the TFA anion and H _2O on the activity and enantioselectivity of catalytic epoxidation. It is found that the TFA anion acts as a counterion to stabilize the transition states of the catalytic epoxidation by hydrogen-bond acceptance, leading to decreases in the barriers of the nucleophilic addition and ring-closure processes. The most significant decrease occurred in the ring-closure step of the Z-R-pathway, resulting in H-bond-induced enantioselectivity. Our calculations also show that water cooperates with TFA to further increase the reaction rate significantly.
收录类别:EI;SCOPUS;SCIE
WOS核心被引频次:7
Scopus被引频次:10
资源类型:期刊论文
原文链接:https://www.scopus.com/inward/record.uri?eid=2-s2.0-84863035754&doi=10.1021%2fjp207914h&partnerID=40&md5=159b9677f6ade750f2f2c96c48191a9c
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