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(3 + 1) Annulation/Rearrangement Cascade of C,N-Cyclic Azomethine Imines and 3-Chlorooxindoles: Construction of Hexahydroindeno[2,1-c]pyrazole Spirooxindole Frameworks

Author:
Peng-Fei Zheng, Rong Zeng, Kun Jiang, Hong-Wei Li, Ying Ye, Chao Mu, Li Shuai, Qin Ouyang, Ying-Chun Chen
Source:
Organic letters 2019 v.21 no.24 pp. 10052-10056
ISSN:
1523-7052
Subject:
ambient temperature, chemical reactions, chemical structure, imines, pyrazoles
Abstract:
The Brønsted base promoted (3 + 1) annulation reaction of C,N-cyclic azomethine imines and 3-chlorooxindoles was investigated, finally delivering complex hexahydroindeno[2,1-c] pyrazoles incorporating a spirocyclic oxindole motif after an unexpected rearrangement process. The asymmetric version of this new transformation could be accomplished, but slow racemization of the chiral product was observed at ambient temperature. Experiments and DFT calculations were further conducted to elucidate the reaction process and racemization mechanism.
Agid:
6792204