Methyl (Z)-4-aryl-2-hydroxy-4-oxobut-2-enoates (methyl aroylpyruvates) reacted with 1,3,3-tri-methyl-2-methylidene-2,3-dihydro-1H-indole (Fischer's base) to give (2Z,5E)-1-aryl-3-hydroxy-5-(1,3,3-tri-methyl-2,3-dihydro-1H-indol-2-ylidene)pent-2-ene-1,4-diones.