Phosphine-Catalyzed Synthesis of Highly Functionalized Coumarins
摘要:
[GRAPHICS]2-Styrenyl allenoates are converted into cyclopentene-fused dihydrocoumarins through phosphine-catalyzed regio- and diastereoselective [3 + 2] cycloadditions. Remarkably, changing the solvent from THF to benzene promotes the conversion of the 2-(2-nitrostyrenyl) allenoate into a tricyclic nitronate through a previously undocumented mode of phosphine catalysis. This nitronate was subjected to efficient face-, regio-, and exo-selective 1,3-dipolar cycloadditions to provide tetracyclic coumarin derivatives.
phenol as a directing group, high regioselectivity, good substrate scope, mild reaction conditions, and high efficiency. To the best of our knowledge, this is the first example of a regioselective C−H alkenylation of unprotected phenols utilizing phenolic hydroxyl group as a directing group. The alkenylation of unprotected tyrosine and intramolecular cyclization are also successfully carried out under
Visible-Light-Induced C(sp<sup>2</sup>)–C(sp<sup>3</sup>) Coupling Reaction for the Regioselective Synthesis of 3-Functionalized Coumarins
作者:Ke Zhang、Li Qiao、Jianwei Xie、Zhenwei Lin、Hanjie Li、Ping Lu、Yanguang Wang
DOI:10.1021/acs.joc.1c00848
日期:2021.7.16
A photocatalysis strategy for the regioselective synthesis of 3-functionalized coumarins is reported. With visible light irradiation, a direct and regioselective C(sp2)–C(sp3) coupling reaction of 3-(2-hydroxyphenyl)acrylates with ethers or thioethers occurs by using Ru(bpy)3Cl2·6H2O as a photocatalyst and TBHP as an oxidant. The cascade process involves alkenylation of the C(sp3)–H bond of ethers
Ruthenium(II)-Catalyzed CH Alkenylations of Phenols with Removable Directing Groups
作者:Wenbo Ma、Lutz Ackermann
DOI:10.1002/chem.201301988
日期:2013.10.4
Cationic ruthenium(II) complexes enabled oxidativealkenylations of phenols bearing easily cleavable directing groups. The optimized catalytic system allowed twofold CH bond activations with excellent chemo‐, site‐, and diastereoselectivities. The double CH functionalization process proceeded efficiently in an aerobic fashion under an atmosphere of ambient air. Detailed mechanistic studies were performed