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The transition metal-catalyzed asymmetric n + 2 cycloaddition reaction with oxy-substituted ketene intermediates remains a synthetic challenge due to the limited availability of suitable ketene precursors. Herein, we report a visible-light-driven, palladium-catalyzed asymmetric 4 + 2 cycloaddition of vinyl benzoxazinanones with siloxyketene intermediates, generating structurally diverse chiral quinolinone derivatives with satisfactory diastereo- and enantioselectivities. The transient generation of siloxyketenes from α-ketoacylsilylanes through visible-light-induced Brook rearrangement is important for the success of the present cycloaddition. The 13 C-labeling experiments reveal a Brook rearrangement pathway involving a 1,3-silyl migration process. The side arm effects of BOX ligand and silyl steric hindrance of α-ketoacylsilanes play crucial roles in the stereoselectivity control, and theoretical calculations provide crucial insights into the stereochemical outcome in the reaction.
Yao et al. (Tue,) studied this question.