Dimethylformamide → 5-chloro-3-ethyl-1-methyl-1h-pyrazole-4-carbaldehyde

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Reaction Conditions

Reaction Steps

POCl3 (236.88 g, 1.543 mol, 144 mL) was added dropwise at 0° C. to DMF (59 g, 0.808 mol). The reaction mixture was then diluted with dichloromethane (200 mL), and: 3-ethyl-1-methyl-1H-pyrazol-5-ol (84.5 g, from Step 1) was added while stirring at 0° C. The mixture was refluxed for 3 h and then stirred overnight at room temperature. After this, ice-cold water (500 mL) was added rapidly at 0° C. to the reaction mixture in order to decompose the formylation agent. The organic layer was separated, and the aqueous phase extracted with chloroform several times. The organic layers were then washed with K2CO3 solution to obtain a weak alkaline media, dried over Na2SO4 and evaporated to give 51.2 g of an oily substance. The residual reaction mass was neutralized with K2CO3 to obtain a weak acidic media and extracted with chloroform. The combined extracts were concentrated and the residue purified by chromatography (dichloromethane) on a silica gel to give 71.3 g (62%) of the title product.

Provenance & Evidence