反应详情

A mixture of zinc powder (712 mg) and dibromoethane (0.04 ml) in N,N-dimethylformamide (2.5 ml) were stirred under heating at 70° C. for 10 minutes under argon atmosphere. The reaction mixture was cooled to room temperature, and chlorotrimethylsilane (0.04 ml) was added thereto, and the mixture was stirred at room temperature for 30 minutes. To the activated zinc solution was added dropwise a solution of 4-ethylbenzyl bromide (1.74 g) in N,N-dimethylformamide (10 ml) at 0° C. over a period of 2 hours. Subsequently, the mixture was stirred at 0° C. for 2 hours, to prepare a solution of 4-ethylbenzylzinc bromide in N,N-dimethylformamide, which was used in the subsequent step without further purification. (2) A solution of tris(dibenzylideneacetone)dipalladium (0) (167 mg) and tri(2-furyl)phosphine (135 mg) in tetrahydrofuran (20 ml) was stirred at room temperature for 5 minutes under argon atmosphere. Thereto were added 1-t-butoxycarbonyl-3-iodo-1H-indazole (2.0 g) and the above 4-ethylbenzylzinc bromide (N,N-dimethylformamide solution) at 0° C., and the mixture was stirred at room temperature for 5 hours. The reaction mixture was poured into water, and the mixture was extracted with diethyl ether. The extract was washed with water and dried over magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate=100:0-92:8) to give 1-t-butoxycarbonyl-3-(4-ethylphenylmethyl)-1H-indazole (1.37 g) as colorless oil. APCI-Mass m/Z 337 (M+H). (3) The above 1-t-butoxycarbonyl-3-(4-ethylphenylmethyl)-1H-indazole (1.35 g) was dissolved in methanol (15 ml), and added thereto was 28% sodium methoxide solution (methanol solution, 1.0 ml), and the mixture was stirred at room temperature for one hour. Added thereto was an aqueous citric acid solution, and the mixture was extracted with ethyl acetate. The extract was washed successively with water and brine, and dried over magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was crystallized from hexane to give the desired 3-(4-ethylphenylmethyl)-1H-indazole (800 mg) as colorless crystals. APCI-Mass m/Z 237 (M+H).

1. additionadded
2. additionAdded
3. extractionthe mixture was extracted with ethyl acetate
4. washThe extract was washed successively with water and brine
5. dry with materialdried over magnesium sulfate
6. customThe solvent was evaporated under reduced pressure
7. customthe residue was crystallized from hexane