Citric Acid → Ethyl 7-bromo-1-(2-((tert-butoxycarbonyl)amino)ethyl)-5-fluoro-1H-indole-2-carboxylate

Beteiligte Stoffe

Reaktionsschritte

To a stirred mixture of sodium hydride [disp. 55-65%] (175 mg, 4.37 mmol) in DMF (5.6 ml) was added drop wise at room temperature under argon atmosphere a solution of commercially available ethyl 7-bromo-5-fluoro-1H-indole-2-carboxylate [CAS No. 396076-60-1] (1.04 g, 3.64 mmol) in DMF (2.8 ml). Afterwards the mixture was allowed to stir for 5 min at room temperature, then commercially available 2,2-dioxo-[1,2,3]oxathiazolidine-3-carboxylic acid tert-butyl ester [CAS No. 459817-82-4] (975 mg, 4.37 mmol) was added and the solution was allowed to stir at room temperature for 15 h. The solution was cooled in an ice bath, and citric acid (10%, 62 ml) was added drop wise. The mixture was allowed to stir at room temperature for 1 h, and was afterwards extracted with ethyl acetate (2×70 ml). The combined organic layers were washed with brine (80 ml), dried (MgSO4) and evaporated. The crude material (2.04 g) was purified by flash chromatography on silica gel (heptan/ethyl acetate 0-80%) to yield 7-bromo-1-(2-tert-butoxycarbonylamino-ethyl)-5-fluoro-1H-indole-2-carboxylic acid ethyl ester as a light yellow oil (1.37 g, 88%), MS (ISN) m/z=431.2 [(M+H)+].

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