Cl[C:2]1[N:6]([CH2:7][CH3:8])[N:5]=[C:4]([CH3:9])[C:3]=1[CH:10]=[O:11].[Cl:12][C:13]1[CH:14]=[C:15]([SH:20])[CH:16]=[C:17]([Cl:19])[CH:18]=1.C(=O)([O-])[O-].[K+].[K+].O>CN(C)C=O>[Cl:12][C:13]1[CH:14]=[C:15]([S:20][C:2]2[N:6]([CH2:7][CH3:8])[N:5]=[C:4]([CH3:9])[C:3]=2[CH:10]=[O:11])[CH:16]=[C:17]([Cl:19])[CH:18]=1
A mixture of 9.2 g of 5-chloro-1-ethyl-3-methyl-1H-pyrazole-4-carbaldehyde, 14.3 g of 3,5-dichlorothiophenol and 11.8 g of potassium carbonate in 40 ml of anhydrous N,N-dimethylformamide was stirred under nitrogen at 100° C. for 18 hours. Water (200 ml) was added and the mixture was extracted three times with 100 ml of dichloromethane. The combined extracts were dried over magnesium sulphate, filtered and evaporated. The residue was purified by flash chromatography on silica gel using dichloromethane/petroleum ether (bp 40-60° C.) for the elution to give 12.2 g of 5-(3,5-dichloro-phenylsulphanyl)-1-ethyl-3-methyl-1H-pyrazole-4-carbaldehyde as an orange solid. Mass spectrum (ES) m/z 356 [M+CH3CN+H]+.
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