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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Sc(OTf)3-Catalyzed (3 + 3) Annulation of Quinoxaline-2(1H)-thiones and Donor-Acceptor Cyclopropanes
Quanyu Ma1, Qingshan Sun1, Ningning Li1
1State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China.
Abstract:
The Sc(OTf)3-catalyzed (3 + 3) annulation of quinoxaline-2(1H)-thiones and donor-acceptor cyclopropanes was achieved in the presence of DBU under air to give functionalized 2,3-dihydro-4H-thiopyrano[2,3-b]quinoxaline derivatives in moderate to high yields. The annulation includes tandem nucleophilic ring opening, nucleophilic addition, and radical oxidative aromatization. It provides not only a new (3 + 3) annulation strategy but also a new synthetic method for fused tricyclic quinoxaline derivatives.
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