Abstract
BackgroundThe plant pathogenic fungus (such as Gibberella zeae, Fusarium oxysporum and Cytospora mandshurica) causes devastating disease in agriculture. The pathogenic fungus is responsible for billions of dollars in economic losses worldwide each year. In order to discover new fungicidal molecule with good fungicidal activity against G. zeae, F. oxysporum, and C. mandshurica, we sought to combine the active sub-structure of hydrazone and pyrazole amide derivatives together to design and synthesize novel pyrazole amide derivatives containing a hydrazone moiety.ResultsA series of novel pyrazole amide derivatives bearing hydrazone moiety were synthesized. Their structures were characterized by 1 H-NMR, 13 C-NMR, IR, and elemental analysis. The preliminary biological assays revealed that most of the synthesized compounds exhibit favorable antifungal activities against G. zeae. The activity of compounds 7a, 7f, 7g, 7h, 7i, 7j, 7l and 7q were 40.82%, 47.78%, 50.32%, 40.82%, 49.05%, 48.73%, 40.19% and 45.89%, respectively, and the synthesized compounds showed certain antifungal activities against F. oxysporum and C.mandshurica.ConclusionA practical synthetic route to pyrazole amide derivatives containing a hydrazone moiety were synthesized by the condensation of intermediates 5-chloro-N-(4-subsititued-2-(hydrazinecarbonyl)-6-methylphenyl)-1,3-dimethyl-1 H-pyrazole-4-carboxamide with different aldehydes or ketones in ethanol at room temperature is presented, the results of the study suggested that the pyrazole amide derivatives containing hydrazone moieties could inhibit the growth of G. zeae, F. oxysporium and C. mandshurica to a certain extent.
Highlights
The plant pathogenic fungus causes devastating disease in agriculture
The fungicidal activity on G. zeae, F. oxysporium and C. mandshurica were evaluated, the results showed that most of the synthesized compounds exhibit favorable antifungal activity against G. zeae and a certain antifungal activity against F. oxysporum and C. mandshurica, of which, compounds 7g and 7i display good activities at 50 mg/L
Intermediates 4 were prepared using 1,3-dimethyl-1 H-pyrazol-5(4 H)-one as starting materials. 1,3-dimethyl-1 H-pyrazol-5(4 H)-one was firstly subjected to Vilsmeier-Haack chloroformylation using N,N-dimethylformamide (DMF) and phosphorus oxychloride (POCl3) to yield 5-chloro-1,3-dimethyl-1 Hpyrazole-4-carbaldehyde 1[9], which was further oxidized by potassium permanganate and following chlorinated with thionyl chloride (SOCl2) to provide the intermediates 3, intermediates 4 were prepared by treating 5-chloro1,3-dimethyl-1 H-pyrazole-4-carbonyl chloride with 2-amino-3-methylbenzoic acid or 5-chloro-2-amino3-methylbenzoic acid in CH2Cl2 in present of triethylamine in good yields, 2-(5-chloro-1,3-dimethyl-1 H-pyrazol-4-yl)8-methyl-4 H-benzo[d] [1,3]oxazin-4-one 5 can be synthesized by reaction of acetic anhydride with 4 in excellent yield [21], it can be prepared in a single step by the reaction of 3 with substituted 2-amino-3methylbenzoic acid as describing in the literature [21,22]
Summary
A series of novel pyrazole amide derivatives bearing hydrazone moiety were synthesized. Their structures were characterized by 1 H-NMR, 13 C-NMR, IR, and elemental analysis. The preliminary biological assays revealed that most of the synthesized compounds exhibit favorable antifungal activities against G. zeae. The activity of compounds 7a, 7f, 7g, 7h, 7i, 7j, 7l and 7q were 40.82%, 47.78%, 50.32%, 40.82%, 49.05%, 48.73%, 40.19% and 45.89%, respectively, and the synthesized compounds showed certain antifungal activities against F. oxysporum and C.mandshurica
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