Hybrid‐Type Squaramide‐Fused Amino Alcohol Organocatalysts for Enantioselective Nitro‐Aldol Reaction of Nitromethane with Isatins

Abstract

A series of hybrid‐type squaramide‐fused amino alcohol (SFAA) catalysts were synthesized, and their catalytic efficiency in the enantioselective nitro‐aldol reaction of various isatins with nitromethane has been described. This transformation afforded chiral 3‐substituted 3‐hydroxyoxindoles in excellent chemical yields (up to 99 %) with high enantioselectivities (up to 95 % ee). The resulting chiral 3‐hydroxyoxindoles can be further used as synthetic precursors for the synthesis of several natural products that have a broad spectrum of fascinating biological activities.