Reaction of pyrimidine-(1H,3H,5H)-2,4,6-trione (barbituric acid), 1,3-dimethyl pyrimidine-(1H, 3H, 5H)-2,4,6-trione (1,3-dimethyl barbituric acid), and 1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (1,3-diethyl thiobarbituric acid) with cyanogen bromide and aromatic dialdehydes in the presence of triethylamine leads to the selective and efficient formation of a novel class of bifunctionalized stable heterocyclic bis-spiro[furo[2,3-d]pyrimidine-6,5'-pyrimidine]2,2',4,4',6'(3H,3'H,5H) pentaones and their sulfur analogues, which are dimeric forms of barbiturate linked by a phenyl ring. A proposed mechanism was suggested for the formation of the products. The reaction of phthalaldehyde with BrCN and (thio)barbituric acids resulted in only monofunctionalized spiro[furo[2,3-d]pyrimidine-6,5'-pyrimidine] 2,2',4,4',6' (3H,3'H, 5H) pentaones, while isophthalaldehyde and terphthalaldehyde resulted in the bifunctionalized form.