Synthesis of 2,2-Disubstituted Indolin-3-ones via Enolonium Species

Herein, we present an efficient and operationally simple one-pot synthesis of a broad range of 2,2-disubstituted indolin-3-ones via the double umpolung reaction of 2-aminophenyl-3-oxopropanoate. The 2-substituent introduced in the reaction may be hydroxy or acetamide. The products can then be functionalized further. The procedure has a broad scope and functional group tolerance. Importantly, density functional theory (DFT) calculations provide novel mechanistic insight into both this and related reactions and reveal that two C-enolonium species are key intermediates of this transformation.