Synthesis and fungicidal activity of novel 3-(substituted/unsubstituted phenylselenonyl)-1-ribosyl/deoxyribosyl-1H-1,2,4-triazole.

Reaction of potassium 1H-1,2,4-triazole-3-selenolate (I) with acetylated ribose/deoxyribose (IIa,b) in the presence of montmorillonite K 10 as a solid adsorbent furnished potassium 1-acetylated ribosyl/deoxyribosyl-1H-1,2,4-triazole-3-selenolate (IIIa,b) with excellent yield under microwave irradiation in solvent-free conditions. This eliminates a series of complex isolation procedures and often minimizes the use of a large amount of expensive, toxic, and hazardous solvents after each step. This procedure reduces reaction time and cost and enhances yield. Reaction of compound (IIIa,b) with substituted/unsubstituted aryl diazonium chloride (IVa-e) at 0-5 °C gave pure 3-(substituted/unsubstituted phenyl selanyl)-1-acetylribosyl/deoxyribosyl-1H-1,2,4-triazole (Va-j). Oxidation of compound (Va-j) with oxone followed by alkaline hydrolysis furnished quantitatively and analytically pure 3-(substituted/unsubstituted phenylselenonyl)-1-ribosyl/deoxyribosyl-1H-1,2,4-triazole (VIIa-j). Compounds VIa-j and VIIa-j were evaluated in vitro for their fungitoxicities against Fusarium oxysporum and Penicillium citrinum. All the compounds were found to be antifungal active. Some of the compounds displayed activities comparable with that of the commercial fungicide Dithane M-45 and griseofulvin. Structure-activity relationships for the screened compounds were discussed. The fact that both of these fungi have developed resistance to several fungicide groups made them optimal candidates as target organisms for ongoing research about the potential application of 1,2,4-triazole and analogue compounds as reduced-risk fungicides.