High-Spin Mn(V)-Oxo Intermediate in Nonheme Manganese Complex-Catalyzed Alkane Hydroxylation Reaction: Experimental and Theoretical Approach
作者:Xiao-Xi Li、Mian Guo、Bin Qiu、Kyung-Bin Cho、Wei Sun、Wonwoo Nam
DOI:10.1021/acs.inorgchem.9b02543
日期:2019.11.4
rebound mechanism; we propose that the triplet spinstate of the Mn(V)-oxo species results from the consequence of breaking the equatorial symmetry due to the binding of an equatorial oxygen from an acetate ligand. Thus, the present study reports that, different from the previously reported S = 0 Mn(V)-oxo species, Mn(V)-oxo species with a triplet groundspinstate are highly reactive oxidants that are responsible
单核非血红素锰配合物是在羧酸存在下通过过氧化氢催化氧化碳氢化合物的高效催化剂。尽管已提出高价的Mn(V)-氧代络合物作为活性氧化剂,在催化氧化反应中具有很高的区域,立体和对映选择性,但自旋态的重要性(例如S = 0或1)提议的Mn(V)-氧代物种中的一个是需要进一步研究的领域。在本研究中,我们从理论上证明了具有S的单核非血红素Mn(V)-氧代物种= 1个基态自旋态是影响立体和对映选择性烷烃羟基化反应的活性氧化剂;应当指出,在光谱和/或结构上表征的合成八面体Mn(V)-氧杂配合物具有S = 0的自旋态并且是缓慢的氧化剂。在实验方法中,我们研究了在羧酸存在下单核非血红素Mn(II)配合物[[ S -PMB)Mn II ] 2+和H 2 O 2对烷烃的催化羟基化作用。醇是具有高立体选择性和对映选择性的主要产品。合成的Mn(IV)-氧配合物[[ S -PMB)Mn IV(O)] 2+,在CH键活化
Catalytic Enantioselective Methylene C(sp<sup>3</sup>)–H Hydroxylation Using a Chiral Manganese Complex/Carboxylic Acid System
作者:Qiangsheng Sun、Wei Sun
DOI:10.1021/acs.orglett.0c03585
日期:2020.12.18
direct C–H hydroxylation in a highly diastereo- and enantioselective manner is still a challenging goal. This reaction is mainly hindered by the potential for overoxidation of the generated alcohols as well as low stereoselectivity. Herein, we present an enantioselective benzylic C–H hydroxylation catalyzed by a manganese complex, H2O2, and a carboxylicacid in 2,2,2-trifluoroethanol. The benzylic alcohols
实现高度非对映和对映选择性的直接C–H羟基化仍然是一个挑战性的目标。该反应主要受到所产生的醇的过度氧化的可能性以及低的立体选择性的阻碍。在本文中,我们介绍了在2,2,2-三氟乙醇中由锰配合物H 2 O 2和羧酸催化的对映选择性苄基C–H羟基化反应。苯甲醇具有出色的非对映选择性(高达> 95:5)和对映选择性(高达95%ee)。作为这项工作的重点,可以通过调整羧酸添加剂的量来实现C–H羟基化的非对映选择性。
Photocatalyzed Triplet Sensitization of Oximes Using Visible Light Provides a Route to Nonclassical Beckmann Rearrangement Products
作者:Xiao Zhang、Tomislav Rovis
DOI:10.1021/jacs.1c10148
日期:2021.12.22
photoisomerization of oximes via visible-light-mediated energy transfer (EnT) catalysis. Facile access to (Z)-oximes provides opportunities to achieve regio- and chemoselectivity complementary to those of widely used transformations employing oxime starting materials. We show an enhanced one-pot protocol for photocatalyzed oxime isomerization and subsequent Beckmannrearrangement that enables novel reactivity with
Highly Enantioselective Oxidation of Spirocyclic Hydrocarbons by Bioinspired Manganese Catalysts and Hydrogen Peroxide
作者:Bin Qiu、Daqian Xu、Qiangsheng Sun、Chengxia Miao、Yong-Min Lee、Xiao-Xi Li、Wonwoo Nam、Wei Sun
DOI:10.1021/acscatal.7b03601
日期:2018.3.2
number of selectiveoxidation reactions over the past several decades. In the present study, we report the enantioselective oxidation of spirocyclic compounds with manganese complexes bearing tetradentate N4 ligands as catalysts and aqueous H2O2 as a terminal oxidant under mild conditions; spirocyclic tetralone (1a) and its derivatives bearing electron-donating and -withdrawing substituents are converted
在过去的几十年中,以生物为灵感的锰配合物已成为许多选择性氧化反应的诱人催化剂。在本研究中,我们报道了在温和条件下,带有四齿N4配体的锰配合物和H 2 O 2水溶液作为末端氧化剂的锰配合物对螺环化合物的对映选择性氧化;螺环四氢萘酮(1a)及其带有给电子和吸电子取代基的衍生物以高收率和对映选择性被转化为它们相应的手性螺环β,β'-二酮。螺环茚满酮也被转化为具有高对映选择性的β,β′-螺双茚满酮。实际上,该反应通过后期的氧化过程扩大了手性螺环二酮的多样性。另外,重要的是要注意催化反应可以容易地扩大规模并且手性螺环β,β′-二酮可以转化为二醇产物。在机理研究中,我们发现(1)酮是通过最初形成醇而生成的产物,然后将醇进一步氧化为酮,(2)从亚甲基C–H提取氢原子(H原子)1a键提出了通过推定的Mn(V)-氧代中间体作为速率确定步骤,并且(3)提出了通过Mn(V)-氧代物种通过氧反弹机制发生1a的C–
An Unexpected Directing Effect in the Asymmetric Transfer Hydrogenation of α,α-Disubstituted Ketones
作者:Rina Soni、John-Michael Collinson、Guy C. Clarkson、Martin Wills
DOI:10.1021/ol201643v
日期:2011.8.19
alpha,alpha-Disubstituted ketones containing an aromatic ring or alkene are reduced in high enantiomeric excess using an asymmetric transfer hydrogenation catalyst. The sense of reduction indicates that the unsaturated region of the ketone adopts a position adjacent to the Ru-bound eta(6)-arene ring in the reduction transition state.