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Asymmetric Synthesis of Spiropyrazolones via Chiral Pd(0)/Ligand Complex-Catalyzed Formal [4+2] Cycloaddition of Vinyl Benzoxazinanones with Alkylidene Pyrazolones

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posted on 2020-12-30, 20:07 authored by Jia-Ming Guo, Xiao-Zu Fan, Hui-Hui Wu, Zhe Tang, Xiao-Fan Bi, Heng Zhang, Lu-Yu Cai, Hong-Wu Zhao, Qi-Di Zhong
In the presence of the chiral Pd(0)/ligand complex, vinyl benzoxazinanones underwent the [4+2] cycloaddition with alkylidene pyrazolones smoothly and delivered spiropyrazolones in reasonable yields, diastereoselectivities, and eneantioselectivities (up to >99% yield, >99:1 dr and 99% ee). The absolute configuration of the obtained spiropyrazolones was unambiguously characterized with the use of X-ray single-crystal structure analysis. Moreover, the reaction mechanism was assumed to interpret the formation of the target compounds.