2-amino-6,7,8,9-tetrahydrobenzo[7]annulen-5-one

Synthesis

93431-20-0

3470-55-1

The general procedure for the synthesis of 2-amino-6,7,8,9-tetrahydro-5H-benzo[7]rotarylen-5-one from the compound (CAS: 93431-20-0) was as follows: polyphosphoric acid (2000 g) mechanically stirred at 100 °C was added to E28B (93.2 g, 396 mmol) in batches over a few minutes. The mixture was stirred at 100 °C for 3 hours. Upon cessation of external heating, although the reaction mixture remains hot, careful batch addition of the ice-water mixture is required to maintain the temperature in the range of 80-100 °C [Note: the reaction is markedly exothermic upon initial addition, and external cooling is used as necessary to maintain the temperature within the specified range]. Continue to add the ice-water mixture until the total volume reaches 4500 mL. subsequently cool the mixture to 0-10°C. Under external cooling, 50% aqueous sodium hydroxide was slowly added, keeping the reaction temperature below 35 °C until the pH of the aqueous phase reached 3-4. The mixture was extracted with ethyl acetate, the organic phases were combined, washed sequentially with saturated aqueous sodium bicarbonate and brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: 0-5% diethyl ether/dichloromethane) and finally crystallized from dichloromethane/hexane to give 58.5 g (84% yield) of the target product, E28C. Its NMR hydrogen spectral (300 MHz, CDCl3) data were as follows: δ 7.69 (d, 1H, J = 8.5 Hz), 6.57 (d, 1H, J = 8.5, 2.2 Hz), 6.47 (d, 1H, J = 2.2 Hz), 2.84 (m, 2H), 2.69 (m, 2H), 1.81 (m, 4H).

References