TiCl₄/DMAP mediated Z-selective knovenagel condensation of isatins with nitroacetates and related compounds

摘要

A highly efficient Z-selective Knovenagel condensation reaction of isatins with nitroacetates mediated by TiCl₄ and DMAP was described. The desired 2-nitro-3-ylideneoxindole acetates were obtained in good to excellent stereoselectivities and yields. Other activated methylene derivatives as well as 4-methylbenzenesulfonamide could provide good results too. This method makes it possible to obtain various unreported 3-ylideneoxindole derivatives under mild reaction conditions.