Reaction of N1,N2-diarylacetamidines 1a - c with 2,3-diphenylcyclopropenone 2 led to formation of addition products 2-methyl-1-aryl-2-arylamino-4,5-diphenyl-1,2-dihydro-3H-pyrrol-3-ones 3a - c. While N1,N2-diarylformamidines 1d - f reacted with 2,3-diphenylcyclopropenone 2 to afford 3-aryl-(N-4-arylformamidoyl)amino-2,3-diphenyl propionic acids 7a - c.