Benzyl Bromide → N-benzyl-3,6-dibromocarbazole

Participants

Reaction Steps

3,6-Dibromocarbazole 2 (112.0 g, 0.344 mol), benzyl bromide (41 ml, 0.344 mol), and nBu4NHSO4 were mixed in 200 ml of acetone and stirred at room temperature under nitrogen until dissolved. KOH (19.3 g, 0.344 mol) was then added to the above transparent solution and the resultant mixture was refluxed for 4 hours, where a white precipitate was observed. The hot mixture was concentrated to remove the majority of acetone. Upon cooling, additional white precipitate appeared. The precipitate was filtered, dissolved in methyl-t-butyl ether, washed with water, dried over Na2SO4, and concentrated to yield a major amount of pure N-benzyl-3,6-dibromocarbazole 3. The filtrate was also washed with water and extracted with methyl-t-butyl ether, dried over Na2SO4, concentrated, and purified over 120 g SiO2 with hexane and hexane:ethylacetate (95:5) eluents to yield a minor amount of pure N-benzyl-3,6-dibromocarbazole 3. The combined yield from crystallization and chromatography was 49 g (35%) of N-benzyl-3,6-dibromocarbazole 3.

Provenance & Evidence