Amide‐phosphonium Salt Catalyzed Enantioselective Vinylogous Mannich Addition of Coumarins to Isatin Imines

An asymmetric vinylogous Mannich reaction between 3-cyano-4-methylcoumarins and N-Boc isatin imines catalysed by amide phosphonium salt is described. This method allows the formation of intriguing adducts bearing both 3-aminooxindole and coumarin moieties in excellent yields with excellent enantioselectivities. The utility of this method was illustrated by a gram scale synthesis using as low as 0.1 mol % of catalyst without chromatographic purification, and removal of the Boc protecting groups on the primary amine functionality in Mannich products.