Synthesis
4-Amino-N,N-dimethylaniline (10.00 g, 73.4 mmol, source: Alfa Aesar) was dissolved in 6 M aqueous hydrochloric acid solution (132 mL). To this solution was added (E)-2-butenal (10.30 g, 147 mmol, source: Acros) and the mixture was stirred at room temperature for 1 hour. Toluene (70 mL) was then added and the reaction mixture was heated to reflux overnight. Upon completion of the reaction, it was cooled to room temperature, and the organic layer was separated and discarded. The aqueous layer was neutralized with 10% sodium hydroxide solution (350 mL) and subsequently extracted with dichloromethane (2 x 100 mL). The organic phases were combined, washed sequentially with water (2 x 100 mL) and saturated aqueous sodium chloride solution (2 x 100 mL), dried over anhydrous sodium sulfate, and concentrated under reduced pressure. Purification by silica gel column chromatography (eluent: ethyl acetate) afforded N,N,2-trimethylquinolin-6-amine 8.44 g (62% yield) as brown solid.1H NMR (500 MHz): δ 7.87 (d, J = 9.3 Hz, 1H), 7.83 (d, J = 8.3 Hz, 1H), 7.31 (dd, J = 9.3, 2.9 Hz, 1H), 7.13 (dd, J = 9.3, 2.9 Hz, 1H), 7.13 (dd, J = 9.3, 2.9 Hz, 1H). 1H), 7.13 (d, J = 8.3 Hz, 1H), 6.76 (d, J = 2.9 Hz, 1H), 3.01 (s, 6H), 2.66 (s, 3H). 13C NMR (125.8 MHz): δ 154.54, 148.12, 141.89, 134.43, 129.10, 127.77, 122.11, 119.30, 105.41, 40.78, 24.92.
References
[1] Organic Letters, 2012, vol. 14, # 24, p. 6366 - 6369
[2] Patent: WO2014/187874, 2014, A1. Location in patent: Page/Page column 25
[3] Patent: CN105018072, 2017, B. Location in patent: Paragraph 0021; 0030; 0031
[4] Patent: CN105001160, 2017, B. Location in patent: Paragraph 0025; 0026; 0027
