Chinese Journal of Catalysis ›› 2022, Vol. 43 ›› Issue (7): 1812-1817.DOI: 10.1016/S1872-2067(21)64051-2

• Communications • Previous Articles     Next Articles

The synthesis of tetracyclic coumarins via decarboxylative asymmetric [4+2] cycloadditions enabled by Pd(0)/Cu(I) synergistic catalysis

Kai Wanga, Xiangfeng Lina,b, Qian Lia,b, Yan Liua,*(), Can Lia,#()   

  1. aState Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 110623, Liaoning, China
    bUniversity of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2022-02-12 Accepted:2022-03-15 Online:2022-07-18 Published:2022-05-20
  • Contact: Yan Liu, Can Li
  • Supported by:
    National Natural Science Foundation of China(21871254);DICP(DICP ZZBS201602);K. C. Wong Education Foundation(GJTD-2020-08)

Abstract:

Tetracyclic coumarins are a class of important compounds with diverse and superior pharmacological activities. However, a direct stereoselective method from simple and readily-made coumarins derivatives remains challenging due to the inertness of coumarins as dienophiles. Herein, we develop a decarboxylative asymmetric [4+2] cycloaddition of 3-cyanocoumarins with vinyl benzoxazinones, affording the coumarin-derived condensed rings bearing three continuous stereocenters in high yields with excellent diastereoselectivities (>20/1 d.r.) and enantioselectivities (up to 99% ee). This direct enantioselective reaction was achieved by a Pd(0)/Cu(I) bimetallic catalytic system. The mechanism studies indicated that the synergistic activation effect, in which chiral Cu(I) as an available Lewis acid catalyst activates 3-cyanocoumarin and chiral Pd(0) complex activates benzoxazinone by the formation of π-allyl-palladium intermediate, plays an important role on the stereoselective control. The current work provides a new activation modes of Cu catalyst in the Pd/Cu bimetallic catalytic system.

Key words: Synergistic catalysis, Pd(0)/Cu(I) catalysis, Asymmetric catalysis, [4+2] Cycloaddition, Tetracyclic coumarins, Chiral catalysis