The carbodiimides 2, obtained from aza-Wittig reactions of vinyl iminophosphorane 1 with aromatic isocyanates, reacted with hydrazine to give 1-amino-2-arylamino-4-arylidene-4,5-dihy-dro-imidazol- 5-ones (4). One-pot reactions of 4 with isocyanates (or acyl chlorides), triphenyl phosphine, hexachloroethane and triethylamine produced 2-anilino (or methyl)-5-arylidene-1-aryl-4,5-dihydroimidazo[1,2-b]- 1',2',4'-triazol-4-ones 6 (or 7) in good yields. The biological activities of the new heterocycles synthesized were investigated and the results showed that some of the compounds exhibited good fungicidal activities. For example, 7c exhibited 100% inhibition against Fusarium oxysporum, Pyricularia oryzae, Botrytis Cinerea Pers., and Sclerotinia sclerotiorum de Bary at 50 mg/L.

Key words: aza-Wittig reaction, carbodiimide, fungicidal activity, 4,5-dihydroimidazo[1,2-b]-1',2',4'-triazol-4-one