Quaternary Carbon Center Forming Formal [3 + 3] Cycloaddition Reaction via Bifunctional Catalysis: Asymmetric Synthesis   of Spirocyclohexene Pyrazolones

Jin-Yu Liu, Jing Zhao, Jia-Lu Zhang, and   Peng-Fei Xu*

https://doi.org/10.1021/acs.orglett.7b00610