1,3-Dipolar cycloaddition reaction of nitrilimines to a variety of 3-aryl-5-arylmethylidene- 3,5-dihydro-2-phenyl-4H-imidazol-4-ones (3) afforded the corresponding 1,3,4,7,8-pentaaryl -1,2,6,8-tetraazaspiro[4.4]-nona-2,6-dien-9-ones (4) and not the regio-isomers 2,3,6,8,9-pentaaryl- 1,3,7,8-tetraazaspiro[4.4]nona-1,6-dien-4-ones (5) in high regioselectivity.