Zhou Yu
2002
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Journal
Fine chemicals
Abstract
3-(4-Chloro 2 fluoro 5 methoxyphenyl) 1 methyl 5 trifluoromethyl 1H pyrazole,an intermediate of herbicides,was obtained from the following steps.Treatment of 4 chloro 2 fluoroanisole with dichloromethyl methyl ether and titanium tetrachloride under ice-water bath gave 4 chloro 2 fluoro 5 methoxybenzaldehyde(Ⅰ).I was converted to 4 chloro 2 fluoro 5 methoxyacetophenone(Ⅱ) by treatment with methyl Grignard followed by oxidation using chromium trioxide under acidic condition.Ⅱreacted with ethyl trifluoroacetate in sodium methoxide/methanol solvent to form 1 (4 chloro 2 fluoro 5 methoxyphenyl) 4,4,4 trifluoro 1,3 butandione(Ⅲ).Ⅲreacted with aqueous hydrazine,and then is methylated using dimethylsulfate to obtain the final product.The total yield was 63 5%.In the last step,methylation with dimethylsulfate,the by product could be reduced if the reaction was carried out under acidic condition.Structures of the products were confirmed by CIMS, 1HNMR and 13 CNMR.