NC1NC2C=CC=CC=2N=1.[C:11](=O)(OC1C=CC=CC=1)[O:12]C1C=CC=CC=1.C1(O)C=CC=CC=1.C(NCCCC)CCC.[N:43]1[C:47]2[CH:48]=[CH:49][CH:50]=[CH:51][C:46]=2[NH:45][C:44]=1[NH:52][C:53]([NH:55][CH2:56][CH2:57][CH2:58][CH3:59])=[O:54].C(=O)([O-])[O-].[K+].[K+]>C(#N)C1C=CC=CC=1.N1C=CC=CC=1>[CH2:56]([N:55]1[C:11](=[O:12])[N:45]2[C:44](=[N:43][C:47]3[CH:48]=[CH:49][CH:50]=[CH:51][C:46]=32)[NH:52][C:53]1=[O:54])[CH2:57][CH2:58][CH3:59]A mixture of 100 g of 2-aminobenzimidazole and 188 g of diphenyl carbonate, 390 g of phenol and 0.1 g of pyridine was kept for 1 hour at 60°-68° C. and for 15 hours at 70° C. 63 g of dibutylamine were added and the reaction mixture was kept for 1 hour at 70° C. and for 3 hours at 100° C. For the reaction, according to the invention, of the resulting 1-(benzimidazol-2-yl)-3-(butyl)-urea, 241 g of diphenyl carbonate, 200 g of benzonitrile and 0.2 g of potassium carbonate, were added and the mixture was heated to 160° C. for 16 hours. The solvent was largely distilled off in vacuo and the residue was mixed with dibutyl ether. 3-Butyl-2,4-dioxo-1,2,3,4-tetrahydro-s-triazino-[1,2-a]-benzimidazole crystallized out as a crude product. This was separated off and washed with dibutyl ether. For purification, the crude product was boiled with 28 g of potassium hydroxide in 3 liters of water for 90 minutes. The hot solution was filtered. 3-Butyl-2,4-dioxo-1,2,3,4-tetrahydro-s-triazino-[1,2-a]-benzimidazole was isolated from the filtrate by acidification to a pH value of about 5. Melting point 275°-280° C.
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