Efficient Assembly of Cyclohexane-Tethered Bispirooxindoles via Carboanion Relay Enabled [1 + 2 + 2 + 1] Annulation

Abstract

A novel carboanion relay enabled [1 + 2 + 2 + 1] cascade cyclization reaction utilizing rarely used isatin-derived β-silylcarbinols and aryl methyl ketones as readily available starting materials has been developed, endowing a powerful platform for the streamline synthesis of cyclohexane-tethered bispirooxindoles in decent yields with high diastereoselectivities. This protocol was realized by merging triple Michael additions and C—C bond cleavage using Cs₂CO₃ as a robust promotor under transition metal-free conditions. The practicability of this method is demonstrated by its simple operation, broad substrate scope as well as easy scale-up.