Asymmetric [3 + 3] Annulation of Copper-Allenylidenes with Pyrazolones: Synthesis of Chiral 1,4-Dihydropyrano[2,3- c]pyrazoles

Organic Letters
Feng JiangHongchao Guo

Abstract

The copper-catalyzed asymmetric [3 + 3] annulation of ethynyl benzoxazinanones with pyrazolones has been achieved, providing simple access to 1,4-dihydropyrano[2,3- c]pyrazole derivatives in moderate to excellent yields with excellent enantioselectivities (up to 99% ee). Compared with previous annulation reactions of copper-allenylidenes from ethynyl benzoxazinanones, the current reaction fused the three carbon atoms of the propargyl moiety into a heterocyclic framework.

References

Apr 12, 2008·Angewandte Chemie·Gaku HattoriYoshiaki Nishibayashi
Dec 3, 2008·Journal of Combinatorial Chemistry·Ying-ming PanZhuang-ping Zhan
Dec 23, 2008·Angewandte Chemie·Natalie Ljungdahl, Nina Kann
May 15, 2009·Chemical Reviews·Victorio Cadierno, José Gimeno
Jun 30, 2016·Journal of the American Chemical Society·Qiang WangWen-Jing Xiao
Apr 4, 2017·Angewandte Chemie·Jin SongLiu-Zhu Gong
Jul 7, 2017·Chemical Communications : Chem Comm·Long Shao, Xiang-Ping Hu

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