[CH3:1]N(C)CCN.C[Al](C)C.C(O[C:14]([C:16]1[CH:17]=[N:18][N:19]([C:21]2[CH:26]=[CH:25][CH:24]=[C:23]([Br:27])[CH:22]=2)[CH:20]=1)=[O:15])C>C1(C)C=CC=CC=1>[Br:27][C:23]1[CH:22]=[C:21]([N:19]2[CH:20]=[C:16]([C:14](=[O:15])[CH3:1])[CH:17]=[N:18]2)[CH:26]=[CH:25][CH:24]=1A solution of N,N-dimethylethylenediamine (1.8 ml, 16.76 mmol) in toluene (30 ml) was treated dropwise at 0° C. under an argon atmosphere with trimethylaluminum (2M in toluene, 22.86 ml, 45.7 mmol). The reaction mixture was stirred at 25° C. for 1 hour before adding 1-(3-bromo-phenyl)-1H-pyrazole-4-carboxylic acid ethyl ester (3.8 g, 12.8 mmol) (CAS 784142-89-8; WO2004092140). The resulting mixture was heated to reflux for 12 hours. For the workup, the mixture was cooled to 25° C., quenched with hydrochloric acid (1N) and extracted with ethyl acetate (3×100 ml). The combined organic layers were washed with brine (50 ml), dried over sodium sulphate and evaporated at reduced pressure. The crude material thus obtained was purified by column chromatography on silica gel using a 9:1-mixture of hexane and ethyl acetate as the eluent to give the 1-[1-(3-bromo-phenyl)-1H-pyrazol-4-yl]ethanone (2.4 g, 83.5%) as an off-white solid. MS (ISP): m/z=310 [M+CH3CN]+.
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