Oxidative Annulation of Arenecarboxylic and Acrylic Acids with Alkynes under Ambient Conditions Catalyzed by an Electron-Deficient Rhodium(III) Complex
It has been established that an electron‐deficient CpE rhodium(III) complex catalyzes the oxidative [4+2] annulation of substituted arenecarboxylic and acrylic acids with alkynes under ambient conditions (at RT–40 °C, under air) without using excess amounts of substrates to produce the corresponding substituted isocoumarins and α‐pyrones in high yields. Minor modification of reaction conditions depending
Rhodium(III)‐Catalyzed, CH Activated Annulation to Form Isocoumarins and
<i>α</i>
‐Pyrones using the ON Bond as an Internal Oxidant
作者:Xing Guang Li、Kai Liu、Gang Zou、Pei Nian Liu
DOI:10.1002/adsc.201400200
日期:2014.5.5
A mild, efficient and regioselective CHactivation‐based intermolecular redox‐neutral annulation of O‐benzoylhydroxylamines and internal alkynes has been achieved. The protocol employs an ONbond as the internaloxidant and leads to isocoumarins and α‐pyrones.
An inexpensive cationic ruthenium(II) catalyst enabled the expedient synthesis of isocoumarins through oxidative annulations of alkynes by benzoic acids. This C-H/O-H bond functionalization process also proved applicable to the preparation of alpha-pyrones and was shown to proceed by rate-limiting C-H bond ruthenation.