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

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.

Automated summary

In the presence of the chiral Pd(0)/ligand complex, vinyl benzoxazinanones smoothly underwent [4+2] cycloaddition with alkylidene pyrazolones to deliver spiropyrazolones in reasonable yields and high diastereoselectivities and enantioselectivities. The absolute configuration of the obtained spiropyrazolones was characterized using X-ray single-crystal structure analysis. A proposed reaction mechanism explained the formation of the target compounds.