Hydrochloric Acid → Lithium diisopropylamide

Participants

Reaction Steps

A lithium diisopropyl amide solution was prepared by adding, at −78° C., a hexane solution of 1.0 M n-butyl lithium to an anhydrous tetrahydrofuran (THF) solution (1.5 ml) of diisopropyl amine (370 μl). The prepared solution was added at −78° C. to a tetrahydrofuran (THF) solution (6 ml) of 4-chloro-1-(toluene-4-sulfonyl)-1H-indole. This was stirred for 15 minutes. After adding methyl chloroformate (169 μl) thereto, the reaction mixture was stirred at −78° C. for 15 minutes, and then an aqueous solution (4 ml) of 1 M hydrochloric acid was added thereto at −78° C. After warming it to room temperature, the reaction mixture was extracted with ethyl acetate (10 ml). The organic layer was washed with an aqueous solution saturated with sodium chloride, and the organic layer was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane/ethyl acetate). Thus, 4-chloro-1-(toluene-4-sulfonyl)-1H-indole-2-carboxylic acid methyl ester was obtained as a colorless solid (591 mg, 82%).

Provenance & Evidence