33332-29-5

5049-61-6

33332-29-5

General procedure for the synthesis of 2-amino-5-chloropyrazine from 2-aminopyrazine: 2-aminopyrazine (23.86 g, 0.2509 mol) was dissolved in dichloromethane (420 mL) and cooled to 0 °C. Subsequently, N-chlorosuccinimide (33.50 g, 0.2509 mol) was added to the solution. The reaction mixture was stirred at 0 °C for 24 hours. Upon completion of the reaction, the reaction mixture was diluted with water (500 mL) and then dichloromethane was removed by vacuum concentration. The progress of the reaction was monitored by thin-layer chromatography using ethyl acetate to continuously extract the aqueous layer until product was no longer detected in the aqueous layer. The organic layers were combined, dried with sodium sulfate, filtered and concentrated in vacuum. Purification by fast column chromatography (Merck silica gel 60, 70-230 mesh, 25% ethyl acetate/hexane) afforded 2-amino-5-chloropyrazine (2.66 g, 8.2% yield) as a yellow solid with a melting point of 126-128 °C; EI-HRMS m/e calculated value of C4H4ClN3 (M+) 129.0094 and measured value of 129.0090. General procedure for the preparation of 2(R)-(3-chloro-4-methylsulfonyl-phenyl)-3-(4-oxo-cyclohexyl)-propionamide: 2(R)-(3-chloro-4-methylsulfonyl-phenyl)-3-(4-oxo-cyclohexyl)-propionic acid (prepared as in Example 60, 200 mg, 0.56 mmol) and triphenylphosphine (192 mg, 0.73 mmol) in A solution of dichloromethane (4.0 mL) was cooled to 0°C and N-bromosuccinimide (128 mg, 0.73 mmol) was added in small portions. After addition, the reaction mixture was slowly warmed to 25 °C over 30 min. Subsequently, 2-amino-5-chloropyrazine (145 mg, 1.12 mmol) and 2,6-dimethylpyridine (0.28 mL, 2.24 mmol) were added, and the reaction mixture was stirred at 25 °C for 4 hours. After completion of the reaction, the reaction mixture was diluted with dichloromethane (25 mL) and washed sequentially with 10% aqueous hydrochloric acid (1 × 20 mL), saturated aqueous sodium bicarbonate (1 × 20 mL) and water (1 × 20 mL). The organic layer was dried over sodium sulfate, filtered and concentrated in vacuum. Purification by Biotage chromatography (FLASH 40S, silica, 13/7 hexane/ethyl acetate to 2/3 hexane/ethyl acetate) afforded 2(R)-(3-chloro-4-methylsulfonyl-phenyl)-N-(5-chloro-pyrazin-2-yl)-3-(4-oxo-cyclohexyl)-propionamide (137 mg, 52% yield) as a light yellow foam: [α] 23589 = -27.35° (c = 0.49, chloroform); EI-HRMS m/e calculated value C20H21Cl2N3O4S(M + H)+ 470.0703, measured value 470.0705.