Rapid Asymmetric Synthesis of Disubstituted Allenes by Coupling of Flow-Generated Diazo Compounds and Propargylated Amines
作者:Jian-Siang Poh、Szabolcs Makai、Timo von Keutz、Duc N. Tran、Claudio Battilocchio、Patrick Pasau、Steven V. Ley
DOI:10.1002/anie.201611067
日期:2017.2.6
We report herein the asymmetric coupling of flow‐generated unstabilized diazo compounds and propargylated amine derivatives, using a new pyridinebis(imidazoline) ligand, a copper catalyst and base. The reaction proceeds rapidly, generating chiral allenes in 10–20 minutes with high enantioselectivity (89–98 % de/ee), moderate yields and a wide functional group tolerance.
A new and highly efficient catalyst for the enantioselective Mukaiyama–Michael reaction between ( E )-3-crotonoyl-1,3-oxazolidin-2-one and 2-trimethylsilyloxyfuran
diastereoselectivity was entirely anti and the enantioselectivity was excellent (ranging from 98 to >99%). A mechanisticinsight into the nature of the activated substrate–catalyst complex was inferred studying the lanthanum complexes with 1H and 13C NMR spectroscopy. Based on these results and on the crystallographic structure of the complex between pybox and La(OTf)3, a stereochemical model is proposed to rationalise
2-三甲基甲硅烷基氧基呋喃与(E)-3-巴豆酰-1,3-恶唑烷-2--2-之间的Mukaiyama-Michael反应已被几种基于双(恶唑啉)(盒)或吡啶双(恶唑啉)的旋光配合物立体选择性催化)(pybox)手性配体和金属阳离子。从新合成的2,6-双衍生的催化剂[(4' - [R,5' - [R )-二苯基-1,3-恶唑啉-2'-基]吡啶和Eu的三氟甲磺酸酯III,拉III,Ce的IV分别为高效:非对映选择性完全抗对映选择性极好(98%至> 99%)。推断出了活化的底物-催化剂配合物的性质的机械机理,用1 H和13 C NMR光谱研究了镧配合物。基于这些结果以及pybox和La(OTf)3之间的配合物的晶体结构,提出了一种立体化学模型,以合理化位置5上取代基的关键作用,适当地放置该化合物以遮蔽配位试剂的Si面。
Chiral Lewis Acid-Catalyzed Enantioselective Cycloadditions between Indoles and Cyclic Carbonyl Ylides Derived from Diazodiketone or Diazoketoester Derivatives
Asymmetric 1,3-dipolar cycloaddition reactions between N-methylindoles and several cyclic carbonyl ylides that were derived from diazodiketone or diazoketoester precursors in the presence of both achiral Rh and chiral lanthanoid metal catalysts are described. For the six-membered cyclic carbonyl ylides derived from 1-diazo-5-aryl-2,5-pentanedione precursors, the cycloaddition reactions were carried out using Rh-2(OAc)(4) (2 mol %) and the chiral Pybox-Ph-2 -Lu(OTf)(3) complex (10 mol %) as catalysts, resulting in high enantioselectivities (83% to >98% ee (exo)) along with relatively good exo-selectivities (exo:endo = 65:35 to 94:6) and yields (63-85%). For the five-membered cyclic carbonyl ylide derived from bromo-1-methylindole was carried out in the presence of Rh-2(OAc)(4) (2 mol%) and chiral Pybox-Ph-2-Er(OTf)(3) complex (30 mol %) as catalysts, resulting in relatively good enantioselectivity (78% ee) and endo-selectivity (endo:exo = 81:19).
Highly Enantioselective Conjugate Addition of Thiols Using Mild Scandium Triflate Catalysis
作者:Aki M. M. Abe、Sami J. K. Sauerland、Ari M. P. Koskinen
DOI:10.1021/jo070492z
日期:2007.7.1
A Sc complex of (4S,5S)-diphenyl PYBOX 1 was found to serve as a catalyst for the asymmetric conjugate addition reactions between various thiols and 3-crotonoyl-2-oxazolidinone, affording the corresponding adducts in good yields and high enantioselectivies (up to 92% ee). A new improved method for making (4S,5S)-diphenyl PYBOX is presented.
Enantioselective Copper Catalyzed Alkyne–Azide Cycloaddition by Dynamic Kinetic Resolution
作者:En-Chih Liu、Joseph J. Topczewski
DOI:10.1021/jacs.9b01091
日期:2019.4.3
The copper(I) catalyzed alkyne-azide cycloaddition (CuAAC), a click reaction, is one of the most powerful catalytic reactions developed during the last two decades. Conducting CuAAC enantioselectively would add a third dimension to this reaction and would enable the direct synthesis of α-chiral triazoles. Doing so is demanding because the two precursors have linear geometries, and the triazole product