Toluene → 9-ethyl-9H-carbazole-3,6-dicarbaldehyde

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Reaction Steps

138.8 g (1.02 mol) of zinc chloride was weighed and put in a 2-liter reaction flask, and 1 liter of toluene was added, followed by dehydration under reflux for 3 hours. The solution was cooled to room temperature, and 100 g (0.51 mol) of ethylcarbazole (4a) (manufactured by Tokyo Kasei Kogyo Co.) and 267.9 g (3.67 mol) of N,N-dimethylformamide were added. Subsequently, 468.3 g (3.05 mol) of phosphorus oxychloride was added elevating the temperature from room temperature to 80° C. over a period of 30 minutes. The flask was heated to 82° C. in an oil bath and stirred for 72 hours. After cooling, the mixture was poured into 5 liters of ice water, and sodium carbonate was slowly added to make the solution basic (pH 10-11). Then, 1 liter of toluene was added, and the resulting solution was stirred at 60° C. for 1 hour. After standing, solution separation was carried out. The toluene phase was washed with water (3 liters×3), dried (MgSO4), and concentrated. The resulting crude crystals (132.1 g) were recrystallized twice from toluene, thus obtaining 79.23 g of 3,6-diformyl-9-ethylcarbazole (2a).

Provenance & Evidence