N-bromobutanimide → 5-bromomethyl-1-tert-butyl-1H-pyrazole-4-carboxylic acid methyl ester

Beteiligte Stoffe

Reaktionsschritte

A solution of 1-tert-butyl-5-methyl-1H-pyrazole-4-carboxylic acid methyl ester (3.38 g, 17.22 mmol) (as described in Example 54, Step 2) in carbon tetrachloride (12.2 mL, 1.41M) at 25° C. was treated with N-bromosuccinimide (3.10 g, 17.41 mmol). The reaction flask was fitted with a reflux condenser. The set-up was wrapped with aluminum foil and was then illuminated with a 250 Watt sun lamp for 3 h. At this time, the reaction was filtered and was rinsed with carbon tetrachloride. The filtrate was transferred to a separatory funnel and was washed with water (1×50 mL) and a saturated aqueous sodium chloride solution (1×50 mL). The organics were dried over magnesium sulfate, filtered, rinsed with carbon tetrachloride and concentrated in vacuo to a light yellow oil. ISCO CombiFlash chromatography (120 g, 0-10% ethyl acetate/hexanes) afforded 5-bromomethyl-1-tert-butyl-1H-pyrazole-4-carboxylic acid methyl ester (4.51 g, 95%) as a clear oil. The material was used without further purification.

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