Trifluoroacetic acid → (R)-6-bromo-4-methyl-3,4-dihydropyrazino[1,2-a]indol-1(2H)-one

Participants

Reaction Steps

A solution of 6.10 g (14.3 mmol) (R)-7-bromo-1-(2-tert-butoxycarbonylamino-1-methyl-ethyl)-1H-indole-2-carboxylic acid ethyl ester in 65 ml dichloromethane was cooled down to 0° C. and treated dropwise with 32 ml (28.7 mmol) trifluoroacetic acid. The cooling bath was removed and after 45 min. stirring at room temperature all volatile components were removed at a rotary evaporator and the remaining oil was dissolved in 35 ml methanol. To this solution, 7.93 g (57.4 mmol) potassium carbonate was added and the reaction was stirred for 16 h. The suspension was poured onto water and ethyl acetate; the organic layer was washed with water, dried over magnesium sulfate, filtered and evaporated. The residue was dissolved in dichloromethane, tert-butyl methyl ether was added and the solution was concentrated at a rotary evaporator until a white precipitate began to form. The suspension was filtered, the solid material was washed with tert-butyl methyl ether and dried under high vacuum to give the desired compound as white crystalline solid. ISP-MS: m/e=2381.1 ([M+H+1]).

Provenance & Evidence