Chiral Iminophosphorane Organocatalyzed Asymmetric Sulfenylation of 3-Substituted Oxindoles: Substrate-Interrelated Enantioselectivities

Catalytic asymmetric sulfenylation of 3-substituted oxindoles has been developed through efficient catalysis by tartaric acid derived chiral iminophosphoranes. With N-(phenylthio)phthalimide as the sulfur source, a wide range of optically active 3-phenylthiooxindoles were obtained in excellent yields (90-99%) and good enantiomeric excess (up to 90% ee). Interestingly, 3-aryl and 3-methyl substituted oxindoles afforded sulfenylated products in S-configuration, whereas substituted oxindoles with 3-arylidene or 3-isobutyl substituents gave the corresponding R-configured sulfenylated products.