Synthesis Of Pyraclostrobin

Pyraclostrobin as a novel strobilurin fungicide with broad spectrum, high efficiency and low toxicity, is environmentally friendly and has a high degree of efficacy selectivity. Its activity is3times than those similar fungicides.So Pyraclostrobin has been widely used.In this paper, an efficient route to prepare Pyraclostrobin was introduced after comparing with the pervious methods. This paper reported the synthesis of Pyraclostrobin by five-step processes with o-nitrotoluene as the starting material, including reduction, acylation, methylation, bromination and etherification. The intermediates and the target product were characterized by’HNMR,13CNMR, and the purity was determined by HPLC.The influence, of reaction conditions was also studied. o-Nitrotoluene was reduced to N-2-methylphenylhydroxyamine in the presence of Zinc and NH4Cl with ratio of1:2:1.1at65℃for15min in76%yield. Methyl N-hydroxy-N-2-rnethylphenylcarbamate was prepared by the acylation of N-2-methylphenylhydroxyamine with NaHC03and methyl chloroformate with the ratio of1:1.5:1at cold temperature for3.5h in99%yield. The methylation of methyl1N-hydroxy-N-2-methylphenylcarbamate was run under reflux for5h in the presence of methyl N-hydroxy-N-2-methylphenylcarbamate, K2CO3and Dimethylsulfate (1:1.5:1.2) in99%yield. The bromination was carried at reflux temperature for7h in the presence of methyl N-methoxy-N-2-methylphenylcarbamate and brominating reagents on a ratio of1:1-1:1.2in90%yield. Finally the etherification was carried out at room temperature for20h in the presence of methyl A-2-bromomethylphenyl-N-methoxycarbamate, K2CO3and1-(4-chlorphenyl)pyrazol-3-ol (1:1.5:1) with yield of92%. This protocol provide several advantages, such as less synthetic steps, cheaper and more available raw materials and simple work-up procedures. In addition, the total yield of the method was62%of the final product.