Stereocontrolled Construction of Tetrahydropyrano[2,3-c]pyrazole Scaffold via an Organocatalyzed Formal [3 + 3] Annulation.
A bifunctional squaramide catalyzed enantioselective formal [3 + 3] annulation reaction with pyrazolin-5-ones and nitroallylic acetates has been developed. Densely substituted tetrahydropyrano[2,3-c]pyrazoles with two adjacent stereogenic centers are obtained in a highly stereocontrolled manner. Representative transformation of the annulation product to a biologically important fused dihydroisoquinoline is achieved without any appreciable loss in the diastereo- and enantioselectivity.
Institute and State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University , Tianjin 300071, P. R. China.
Yin
Y
Zheng
Institute and State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University , Tianjin 300071, P. R. China.
Lei
L
Cui
Institute and State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University , Tianjin 300071, P. R. China.
Youming
Y
Wang
Institute and State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University , Tianjin 300071, P. R. China.
Zhenghong
Z
Zhou