[CH3:1][C:2]1[CH:6]=[CH:5][N:4]([C:7]2[CH:12]=[CH:11][C:10]([C:13](Cl)=[O:14])=[CH:9][CH:8]=2)[N:3]=1.[H][H].NC(N)=S>C1(C)C(C)=CC=CC=1.[Pd].[O-]S([O-])(=O)=O.[Ba+2]>[CH3:1][C:2]1[CH:6]=[CH:5][N:4]([C:7]2[CH:12]=[CH:11][C:10]([CH:13]=[O:14])=[CH:9][CH:8]=2)[N:3]=1Using the method of Rosenmund, 88 g of the above 3-methyl-1-(4-chloroformylphenyl)pyrazole are hydrogenated with hydrogen at 140° C. in 900 ml of xylene with the addition of 0.23 g of thiourea and 9 g of Pd/BaSO4 (5%). After cooling to 80° C. and removing the catalyst by filtration, the xylene solution is evaporated to dryness and the precipitated product is recrystallised from a mixture of hexane and toluene, affording 68.3 g of 3-methyl-1-(4-formylphenyl)pyrazole in the form of pale yellow crystals with a melting point of 96°-98° C.
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