Sodium Carbonate → Pyrrole-2-carboxaldehyde

Beteiligte Stoffe

Reaktionsschritte

To cold dimethylformamide (11.1 g) was slowly added phosphorous oxychloride (23.2 g). The resultant clear complex was stirred one hour at ambient temperature and thereafter a solution of N-ethyl-N-(1H-pyrrol-1-yl)-4-pyridinamine (20.5 g) in 135 ml of dichloroethane was added. After stirring twelve hours at 95° the reaction mixture was cooled and hydrolyzed for one hour at 95° with a solution of sodium acetate trihydrate (40 g) in 150 ml of water. The reaction mixture was cooled, basified with sodium carbonate and extracted with dichloromethane. The organic extract was washed with water and saturated sodium chloride solution and thereafter dried over anhydrous magnesium sulfate, filtered and evaporated to 24 g of an oil. This oil was purified first by flash chromatography (silica, dichloromethane, then 10% ethyl acetate in dichloromethane), then by high-pressure liquid chromatography (silica, ethyl acetate) to give 8 g of the pyrrole-2-aldehyde as an oil and 8 g of the pyrrole-3-aldehyde as an oil. 2.5 g of the pyrrole-2-aldehyde was converted to the hydrochloride salt in 2-propanol to give 2.2 g of crystals, mp 214°-215° C.

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