烯烃的催化胺化是构建具有氮中心的复杂杂环最有吸引力的反应之一。在这里,我们提出协同光氧化还原和钴肟催化允许在没有外部氧化剂的情况下,各种 NH 亲核试剂与二、三和四取代烯烃之间进行高效和温和的脱氢反应,从而能够获得一系列N杂环。值得注意的是,含Z和E烯烃的N杂环都是可以得到的。机理研究表明Z-肉桂基衍生物可以通过光催化E to Z通过能量转移过程进行烯烃异构化。此外,我们发现缓慢的能量转移可以抑制E到Z烯烃异构化过程,从而提供具有E选择性的肉桂基衍生物。我们的结果突出了使用双光氧化还原和钴肟催化反应产生多种N-杂环的好处。
Formal Aza‐Wacker Cyclization by Tandem Electrochemical Oxidation and Copper Catalysis
作者:Xiangli Yi、Xile Hu
DOI:10.1002/anie.201814509
日期:2019.3.26
In oxidative electrochemical organic synthesis, radical intermediates are often oxidized to cations on the way to final product formation. Herein, we describe an approach to transform electrochemically generated organic radical intermediates into neutral products by reaction with a metalcatalyst. This approach combines electrochemical oxidation with Cu catalysis to effect formal aza‐Wacker cyclization
N-aryl-4-vinyloxazolidin-2-ones. The success of the reaction depends on the acidity of the aniline and requires in situ conversion of the dicarbonate into carbamate carbonate by nucleophilicattack of the aniline conjugate base followed by palladium-catalyzed intramolecular cyclization.
Palladium(0)-Catalyzed Asymmetric Cycloaddition of Vinyloxiranes with Heterocumulenes Using Chiral Phosphine Ligands: An Effective Route to Highly Enantioselective Vinyloxazolidine Derivatives
作者:Chitchamai Larksarp、Howard Alper
DOI:10.1021/ja964335l
日期:1997.4.1
Cycloaddition reaction of 2-vinyloxiranes with carbodiimides using Pd2(dba)3·CHCl3, and TolBINAP as the chiral ligand, in THF at ambient temperature, afforded 4-vinyl-1,3-oxazolidin-2-imines in 70−99% yield and in up to 95% ee. The stereoselectivity is strongly influenced by the structure of the chiral phosphine ligands and substrates, as well as by the reaction conditions. The enantiodetermination
Direct C–H/N–H dehydrogenative coupling is a promising yet thermodynamically unfavorable transformation in the absence of a sacrificial hydrogen acceptor. Herein, a conceptually novel oxidant-free dehydrogenative amination of alkenes through a synergistic photoredox and cobaltcatalysis with H2 evolution has been achieved. With this approach, a wide range of five-membered N-heterocycles were synthesized
A correlation study of bisphosphine ligand bite angles with enantioselectivity in Pd-catalyzed asymmetric transformations
作者:Malati Raghunath、Xumu Zhang
DOI:10.1016/j.tetlet.2005.09.093
日期:2005.11
Among the bisphosphine ligands, we have previously developed C-n-TunePhos (n = 1-6) as a family of ligands with tunable bite angles. The increase in spacer-CH2- groups in this family of ligands causes changes in ligand dihedral angle, which in turn causes P-Pd-P bite angle variation. Pd-catalyzed asymmetric alkylations and cycloadditions have been tested with C-n-TunePhos ligands. This study aims at a possible correlation between ligand bite angles with enantioselectivity of the Pd-catalyzed asymmetric products. (c) 2005 Published by Elsevier Ltd.