Title:Manganese-Catalyzed Radical 6-endo Azacyclization of 2-Alkynylbenzamide
for the Synthesis of 3-Hydroxylisoquinolin-1,4-dione
Volume: 2
Issue: 5
Author(s): Xiya Cheng, Xiaoyang Yan, Meng Li, Sarita Yadav, Yanfei Lin*Guanyinsheng Qiu*
Affiliation:
- College of Biological, Chemical Sciences and Engineering,
Jiaxing University, Jiaxing 314001, China
- College of Biological, Chemical Sciences and Engineering,
Jiaxing University, Jiaxing 314001, China
Keywords:
2-Alkynylbenzamide, manganese catalysis, hydroxyliosoquinolin-1, 4-dione, 6-endo-dig cyclization, catalyst, MnO2.
Abstract:
Background: The versatile 2-alkynylbenzamde has been reported to produce many privileged
skeletons, like isoquinolin-1-ones, isocoumarin-1-imines, isoindolin-1-ones, and isobenzofuran-
1-imines. Recently, we reported the projected transformation using copper salt (CuCl2) as a
catalyst under the O2 atmosphere. To expand the scope of the reaction, we used another inexpensive
metal salt, MnO2, as a catalyst.
Methods: The paper aims to explore a manganese-catalyzed reaction of 2-alkynylbenzamide under
an O2 balloon for the synthesis of 3-hydroxylisoquinolin-1,4-dione.
Results: Results on reaction scope shows the 10 mol% MnO2 in O2 atmosphere and DCE solvent
catalyzed the cyclization of 2-alkynylbenzamide to produce 3-hydroxylisoquinolin-1,4-diones in
40-68% isolated yields. The reaction proceeds through a regioselective N-center radical 6-endo-dig
aza-cyclization pathway.
Conclusion: We have developed a manganese-catalyzed cyclization of 2-alkynlbenzamide for the
synthesis of 3-hydroxylisoquinolin-1,4-diones under an O2 balloon. It is believed that the N-center
radical-based 6-endo dig aza-cyclization proceeded in a regioselective manner.
