Xiao-Xiong Lv, Ning Liu,* Fei Chen, Hao Zhang, Zhi-Hong Du,* Pei Wang, Meng Yuan and Chao Shan Da. Org. Biomol. Chem., 2023, 21, 8695-8701

Abstract
Herein, we have reported an environmentally friendly asymmetric aldol reaction between isatins and ketones catalyzed by double-hydrogen-bonded primary amine organocatalysts on water under mild conditions. Enantioenriched 3-hydroxy-2-oxindoles were obtained in high yields (up to 99%) and excellent stereoselectivities (up to 99 : 1 dr and 99% ee) under optimal conditions. Furthermore, the model reaction involving isatin and cyclohexanone was successfully scaled to 10 mmol with no reduction in yield or stereoselectivity. In addition, the catalyst was recovered via simple filtration and was subsequently reused on water, which highlights its good application potential.