PURPOSE: To produce the title compound useful as an intermediate for fungicide against blight and downey mildew, in short step and high yield, by using a Vilsmeier reagent derived from dimethylformamide and phosphorus oxychloride and reacting the reagent with a hydrazone derivative.
CONSTITUTION: Dimethylformamide is made to react with phosphorus oxychloride and the obtained so-called Vilsmeier reagent is reacted with a hydrazone derivative of formula I (R1 and R2 are lower alkyl) (e.g., acetone methylhydrazone) to obtain a 1,3-dialkylpyrazole of formula II (e.g., 1,3- dimethylpyrazole-4-aldehyde). Preferably, the amount of dimethylformamide is 1.0W5.0mol per 1mol of phosphorus oxychloride and that of the phosphorus oxychloride is 1.6W3.0mol per 1mol of the hydrazone derivative.
TOMITANI KANJI
SHIMOTORI HITOSHI
TANAKA YOSHINORI
ISHIKAWA KATSUTOSHI
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