Manganese complexes with non-porphyrin N<sub>4</sub>ligands as recyclable catalyst for the asymmetric epoxidation of olefins
作者:Nabin Ch. Maity、Prasanta Kumar Bera、Debashis Ghosh、Sayed H. R. Abdi、Rukhsana I. Kureshy、Noor-ul H. Khan、Hari C. Bajaj、E. Suresh
DOI:10.1039/c3cy00528c
日期:——
complexes of N4 ligands derived from 2-acetylpyridine were prepared and used as catalysts in the enantioselectiveepoxidation of olefins, using H2O2 as an oxidant to give epoxides, with excellent conversions (up to 99%) and enantiomeric excess (up to 88%) within 1 h at 0 °C. A detailed mechanistic study was undertaken based on the information obtained by single crystal X-ray, optical rotation, UV-Vis
制备了由2-乙酰基吡啶衍生的N 4配体的新手性锰配合物,并用作烯烃的对映选择性环氧化的催化剂,使用H 2 O 2作为氧化剂生成环氧化物,具有优异的转化率(高达99%)和对映体过量(最高88%)在0°C下1小时内。根据单晶X射线,旋光,UV-Vis,CD光谱和动力学研究获得的信息进行了详细的机理研究,结果表明该反应对于催化剂和氧化剂的浓度是一阶的,并且是独立的。底物浓度。配合物(0.1 mol%)已成功进行了3个循环的苯乙烯与H 2 O环氧化的可循环性实验2在0°C时作为氧化剂和乙酸作为添加剂,并保持了性能。
Synthesis, applications and mechanistic investigations of C2 symmetric guanidinium salts
作者:Matthew T. Allingham、Elliot L. Bennett、Deniol H. Davies、Philip M. Harper、Andrew Howard-Jones、Yassin T.H. Mehdar、Patrick J. Murphy、Dafydd A. Thomas、Peter W.R. Caulkett、David Potter、Casey M. Lam、AnnMarie C. O'Donoghue
DOI:10.1016/j.tet.2015.11.058
日期:2016.1
epoxidation of somechalcones in 85–94% ee. Using a spectrophotometric method, pKa values in the range 13.2–13.9 in DMSO have been determined for some of the catalysts highlighting an increase in basicity relative to achiral tetramethylguanidine (pKa=13.0) and a mechanism involving the protonated guanidinium ion as a phase transfer catalyst is proposed. The use of two of the catalysts for the addition of nucleophiles
在六个或七个合成步骤中制备了一系列胍鎓催化剂,并用于21-86%ee的甘氨酸Schiff碱的相转移烷基化,以及85-94%ee的一些查耳酮的相转移环氧化。使用分光光度法,对于某些催化剂,确定了DMSO中p K a值在13.2–13.9范围内,从而突出了相对于非手性四甲基胍的碱度增加(p K a= 13.0),提出了一种以质子化的胍鎓离子作为相转移催化剂的机理。研究了使用两种催化剂在迈克尔加成反应中添加亲核试剂,发现两者都是有效的催化剂。在这些反应中抗衡离子作用是明显的,但是没有观察到对映选择性。
One-pot production of chiral α,β-epoxy ketones from benzaldehydes and acetophenones by recyclable poly(amino acid) catalysis
one-pot, two-step process was disclosed for production of chiral α,β-epoxy ketonesfrom benzaldehydes and acetophenones catalyzed by imidazolium-modified poly(l-leucine). Two effective reaction systems with complementary high enantioselectivities (up to 98% ee) or satisfactory yields (up to 89%) have been developed. Importantly, the poly(aminoacid) catalyst can be easily recovered and recycled for ten
4-Substituted-α,α-diaryl-prolinols Improve the Enantioselective Catalytic Epoxidation of α,β-Enones
作者:Yawen Li、Xinyuan Liu、Yingquan Yang、Gang Zhao
DOI:10.1021/jo0617619
日期:2007.1.1
To seek novel metal-free organic catalysts for epoxidation with high stereoselectivity, a series of 4-substituted-α,α-diaryl-prolinols were synthesized in four steps from trans-4-hydroxyl-l-proline. These prolinol derivatives catalyzed the asymmetric epoxidation of α,β-enones to give the corresponding chiral epoxides in good yields and high enantioselectivities under mild reaction conditions. Studies
Asymmetric Epoxidation of Enones Promoted by Dinuclear Magnesium Catalyst
作者:Joanna A. Jaszczewska‐Adamczak、Jacek Mlynarski
DOI:10.1002/adsc.202100482
日期:2021.9.7
still a challenging task. In this perspective, we present the application of chiral dinuclear magnesium complexes for asymmetricepoxidation of a broad range of electron-deficient enones. We demonstrate that the in situ generated magnesium-ProPhenol complex affords enantioenriched oxiranes in high yields and with excellent enantioselectivities (up to 99% ee). Our extensive study verifies the literature