Thionyl Chloride → Ethyl 5-(chlorocarbonyl)-1-ethyl-1H-pyrazole-4-carboxylate

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Reaction Steps

2-Ethyl-2H-pyrazole-3,4-dicarboxylic acid 4-ethyl ester (example 62, step 3, 1.47 g, 6.93 mmol) and thionyl chloride (19.0 g, 11.6 ml, 159 mmol) were combined to give a light yellow solution. The reaction mixture was stirred at reflux for 5 h. Excess thionyl chloride was removed under reduced pressure, and residual thionyl chloride was removed under vacuum. The title compound (1.6 g, estimated purity 37%, 37% yield) was used without further purification in the next step. MS (m/e)=390.3 [M+H+].

Provenance & Evidence