Dimethylformamide → HCID 57360982, compound

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Reaction Steps

To a stirred solution of 1-(2-chloro-phenyl)-5-hydroxy-1H-pyrazole-3-carboxylic acid ethyl ester I-1a (18.2 g) and phosphorus oxybromide (39 g) in 1,2-dichloroethane (200 ml) was added dimethylformamide (10.5 ml) over a 15-min period. The resulting mixture was heated at reflux for 3 hours, cooled, then an additional portion of phosphorus oxybromide (98 g) was added and refluxing was continued for 20 hours. The black reaction mixture was cooled, poured over ice (150 g) and stirred for 30 minutes. The mixture was extracted with dichloromethane (2×), the combined organic layers dried over magnesium sulfate and concentrated in vacuo to afford a dark oil. The oil was passed through a 200 g plug of silica gel, elueting with 30% hexanes:dichloromethane to afford the title compound (I-1b) as a yellow solid, 8.3 g.

Provenance & Evidence