Synthesis And Fungicidal Activities Of 5-Disubstituted Novel Imidazolinones

Imidazolones have been found to show fungicidal, herbicidal, pestcidal and medicinal activities, and have the applied foreground extensively. In this paper, we studied the synthesis of novel imidazolones by utilizing aza-Wittig reaction that has the advantage of easily accessible starting material, mild condition and good yields. The spectral properties, biological activities and the condition for cyclization of imidazolones were also researched and some of them were found to show good fungicidal activities. Sixty four unreported imidazolones in five series were synthesized. It may be summarized as follows:1. The mechanism of iminophosphorane 1 reacted with isocyanates was studied. The results of the experiments showed that iminophosphorane 1 reacted with aromatic isocyanates to give unexpectedly a mixture of carbodiimides 2, 9 and 10 via normal and abnormal aza-Wittig reactions.2. The reactions of carbodiimide 2 reacted with primary amines were studied further. The results showed that carbodiimide 2 reacted with primary amines bearing large steric groups to provide 2-alkylamine-3-alry-4H-imidazol-4-ones, while reacting with non-sterically primary amines give rise to 3-alkyl-2-(alryimino)imidazolidin-4-ones.3. The cyclization reactions of carbodiimide 2 with phenols and alcohols were studied further. The results showed that carbodiimide 2 reacted with phenols can smoothly finished in the presence of solid potassium carbonate at room temperature or 40℃. While more stronger alkali alcoholic sodium are needed when reacting with alcohols.4. Intermediate isothiocyanate 15 was firstly synthesized from aza-Wittig reaction of iminophosphorane 1 with CS₂. By contrast with traditional methods, it has the advantages of easily accessible starting material, mild conditions and low toxicity. The application of aza-Wittig reaction in organic synthesis was enlarged greatly.5. 2-Alkylthio-5,5-dimethyl-4H-imidazol-4-ones were synthesized via aza-Wittig reaction in very mild conditions. The results showed that intermidiate thiosemicarbazide16 can't cyclize atomatically, the cyclization of 16 and the S-alkylation of imidazolidione17 can be finished simultaneously in the presence of solid potassium carbonate, which reduced the experimental process and increased the use ratio of materials. 6. The reaction of isothiocyanate 15 with hydrazine was studied further. The results showed that the isothiocyanate react quickly with hydrazine at room temperature. The product was identified as the five-membered ring compound 3-amino-2-thioxo-4-imi- dazolidinone instead of six-membered ring compound. Then we synthesized imidazol[2,1-b]-1,3,4-thiodiazol-5(6H)-ones via aza-Wittig reaction in very mild conditions.7. The cyclization of the carbodiimide 2 with hydrazine was studied. It was proved that the product was five-membered ring compound 2-arylamino-3-amino-4H-imidazol- 4-one but not its isomeric six-membered ring compound. Then 3,5,-dihydro-6H- imidazol[1,2-b]-1,2,4-triazol-6-ones were synthesized via aza-Wittig reaction in very mild conditions.8. The biological activities of partial imidazolones were studied. The results showed thatâ…°) 2-aryl (alkyl)oxy-5,5-dimethyl-4H-imidazol-4-ones had good fungicidal activities. At 50rag/L, the fungicidal activity of compound 12k against Rhizoctonia solani and Dothiorella gregaria were 78% and 65%, respectively. 12e against Rhizoctonia solani was 61%.â…±) Imidazol[2,1-b]-1,3,4-thiodiazol-5(6H)-ones show moderate fungicidal activities. At 50 mg/L, the fungicidal activity of compound 26f against Rhizoctonia solani and Fusarium oxysporium were 71% and 52%, respectively. 26a against Rhizoctonia solani was 72%.â…²) 3,5,-Dihydro-6H-imidazol[1,2-b]-1,2,4-triazol-6-ones show moderate fungicidal activities. At 50 mg/L, the fungicidal activity of compound 31a against Fusarium oxysporium and Gibberella zeae were 71% and 70%, respectively.