58% |
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Azo-3CN was synthesized following modified two-step procedures as described in the literature [15]. (1) Diazotization: A solution of 4-amino-3,5-dichlorobenzonitril (3mmol) in 10mL ethanol with sulfonic acid (9mmol) was cooled to 4C and a solution of sodium nitrite (4mmol) in 1mL water was added dropwise to the solution. The resulting mixture was stirred for 6h on ice bath. Then the solution of diazonium salt was reacted with 2-(methylphenylamino)ethanol (3mmol) in ethanol at 4C for 12h. The reaction mixture was poured into water and the precipitate was filtered. The red powder was purified by recrystallization in methanol. Yield: 58%; 1H NMR (300MHz, CDCl3): delta=3.16 (s, 3H), 3.67 (t, 2H, J=3.2Hz), 3.91 (t, 2H, J=3.3Hz), 6.84 (d, 2H, J=6.6Hz), 7.67 (s, 2H), 7.91 (d, 2H, J=6.6Hz) ppm. (2) Cyanation: A solution of Azo-3Cl (7mmol) in 20mL anhydrous DMF with copper(I) cyanide (CuCN, 15mmol) was purged with argon gas for 1h. After purging, the mixture was stirred at 130C for 6h. Then the reaction mixture was extracted with water/chloroform. The organic layer was drying with MgSO4 and evaporated under reduced pressure. The purple solid was purified by silica column with eluent chloroform/ethyl acetate (5:1). Yield: 31%; 1H NMR (300MHz, DMSO-d6): delta=2.47 (m, 3H), 3.19 (s, 2H), 3.62 (s, 2H), 7.0 (d, 2H, J=7.2Hz), 7.82 (d, 2H, J=6.9Hz), 8.7 (s, 2H) ppm; 13C NMR (75MHz, DMSO-d6): delta=54.59, 58.56, 106.89, 110.08, 113.13, 115.68, 116.26, 142.62, 155.64, 157.16ppm; HR-MS (ESI+): m/z: calcd for C18H14N6O: 330.12 [M+]; found: 329.11. |