The isomerization of epoxides to aldehydes using the readily available Crabtree's reagent is described. The aldehydes were transformed into synthetically useful amines by a one‐pot reductive amination using pyrrolidine as imine‐formation catalyst. The reactions worked with low catalyst loadings in very mild conditions. The procedure is operationally simple and tolerates a wide range of functional groups
Copper-Catalyzed Enantiotopic-Group-Selective Allylation of <i>gem</i>-Diborylalkanes
作者:Minjae Kim、Bohyun Park、Minkyeong Shin、Suyeon Kim、Junghoon Kim、Mu-Hyun Baik、Seung Hwan Cho
DOI:10.1021/jacs.0c11750
日期:2021.1.20
We report a copper-catalyzed enatiotopic-group-selective allylation of gem-diborylalkanes with allyl bromides. The combination of copper(I) bromide and H8-BINOL derived phosphoramidite ligand proved to be the most effective catalytic system to provide various enantioenriched homoallylic boronate esters, containing a boron-substituted stereogenic center that is solely derived from gem-diborylalkanes
spirocyclization forming spirooxindoles and spirodihydrobenzofurans has been achieved. Mechanistic studies suggest that the transformation proceeds through sequential carbopalladation, C–Hactivation, and benzyne insertion. Both classes of spirocycles have been synthesized in good to excellent yields, and the procedure is readily scalable.
Traversing Steric Limitations by Cooperative Lewis Base/Palladium Catalysis: An Enantioselective Synthesis of α‐Branched Esters Using 2‐Substituted Allyl Electrophiles
作者:Kevin J. Schwarz、Colin M. Pearson、Gabriel A. Cintron‐Rosado、Peng Liu、Thomas N. Snaddon
DOI:10.1002/anie.201803277
日期:2018.6.25
Cooperative catalysis enables the direct enantioselective α‐allylation of linear prochiral esters with 2‐substituted allyl electrophiles. Critical to the successful development of the method was the recognition that metal‐centered reactivity and the source of enantiocontrol are independent. This feature is unique to simultaneous catalysis events and permits logical tuning of the supporting ligands
Unexpected Extension of Usage of PPh<sub>3</sub>/CBr<sub>4</sub>, a Versatile Reagent: Isomerization of Aromatic Allylic Alcohols
作者:Wanchun Gong、Yun Liu、Jijun Xue、Zhixiang Xie、Ying Li
DOI:10.1246/cl.2012.1597
日期:2012.12.5
The PPh3/CBr4-catalyzed isomerization of 2-aromatic allylicalcohols into the corresponding saturated aldehydes or ketones has been achieved at room temperature in good to excellent yields under mild and metal-free conditions. This new methodology has been applied successfully to the synthesis of ibuprofen in four steps.