Benzenesulfonyl fluoride → 4-(2-benzenesulfonyl-1-methyl-1H-indol-4-yl)-piperazine-1-carboxylic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

To a −75° C. solution of 4-(1-methyl-1H-indol-4-yl)-piperazine-1-carboxylic acid tert-butyl ester compound 3-1 (330 mg, 1.05 mmol) in THF (25 mL) was slowly added t-BuLi (1.2 mL, 2.1 mmol). The reaction mixture was stirred for 30 minutes at −75° C. then warmed in an ice bath for 15 min. The reaction was re-cooled to −75° C. and benzenesulfonyl fluoride was added (0.2 mL, 1.6 mmol). The reaction was stirred cold for 1.5 h at which time the ice bath was removed and the reaction was allowed to warm to room temperature (45 min.). The reaction was quenched with a saturated solution of ammonium chloride (55 mL) and extracted with ethyl acetate (3×20 mL). The combined ethyl acetate layers were washed with brine (25 mL), dried (MgSO4), filtered and concentrated to afford a yellow oil. The oil was chromatographed over silica eluting with hexanes/ethyl acetate (4:1) to afford 190 mg (40%) of 4-(2-benzenesulfonyl-1-methyl-1H-indol-4-yl)-piperazine-1-carboxylic acid tert-butyl ester (3-2).

Provenance & Evidence