Dibromomaleimide → 2-bromo-3-(5,6-methylenedioxy-1H-indol-3-yl)maleinimide

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Reaction Steps

6.44 g (40 mmol) 5,6-methylenedioxyindole are dissolved in 300 ml anhydrous toluene and mixed dropwise at 60° C. with 20 ml of a 2M solution of ethyl magnesium bromide in tetrahydrofuran (Aldrich). After completion of the addition, there is added dropwise thereto a solution of 1.7 g (6.67 mmol) dibromomaleinimide in 50 ml toluene, with the addition of the minimum amount of tetrahydrofuran required for solution, and then heated under reflux for 18 hours. After cooling, the reaction mixture is mixed with a saturated aqueous solution of ammonium chloride, the organic phase is separated off and the aqueous phase is extracted three times with toluene and once with ethyl acetate. The combined organic phases are dried, rotary evaporated and chromatographed in silica gel (elution agent: dichloromethane/ethyl acetate 30:1 v/v). There is obtained 1.27 g (56% of theory) 2-bromo-3-(5,6-methylenedioxy-1H-indol-3-yl)maleinimide; m.p. about 185° C. (decomp.); RF=0.50 (dichloromethane/ethyl acetate 3:1 v/v); and 0.63 g (22.5% of theory) 2,3-bis-(5,6-methylenedioxy-1H-indol-3-yl)-maleinimide in the form of red crystals; m.p, about 270° C. (decomp.), after recrystallisation from propanol; RF=0.36 (dichloromethane/ethyl acetate 3:1 v/v).

Provenance & Evidence