反应详情

温度

0 °C

To a solution of 2,2,6,6-tetramethylpiperidine (TMP) (43.8 mL, 36.4 g, 0.258 mol, 1.18 eq.) in anhydrous THF (600 mL), cooled to −78° C., 2.5 M n-BuLi in hexanes (110.9 mL, 0.277 mol, 1.27 eq.) was added directly. The solution was allowed to warm to 0° C. for 20 min, after which the reaction was again cooled to −78° C. A solution of chloropyrazine (19.2 mL, 25.0 g, 0.218 mol) in THF (50 mL) was added dropwise over 10 min; a color change from light yellow to dark brown was observed. The reaction was allowed to react at −78° C. to −70° C. for 10 min. A solution of DMF (42.0 mL, 39.9 g, 0.546 mol, 2.5 eq.) in THF (50 mL) was added slowly over 12 min. The temperature was maintained at −78° C. to −70° C. for 2 h. The reaction was quenched with MeOH (400 mL) at −78° C. and charged with NaBH4 (16.5 g, 0.437 mol, 2.0 eq.) at 0° C. for 2 h. The solvent was partially removed in vacuo and additional CH2Cl2 (200 mL) was added to the oil and the reaction mixture was quenched with 2N HCl (900 mL) to a neutral pH. The aqueous layer was extracted with CH2Cl2 (4×) and EtOAc (2×). The organic layers were combined, dried over Na2SO4, filtered, and concentrated in vacuo, giving a crude black liquid. The crude material was adsorbed onto silica gel (for dry loading) and purified by chromatography on silica gel [2 kg silica gel, eluting with MeCN:CH2Cl2 2%→5%→10%] affording the title compound, as a dark brown oil; 1H NMR (400 MHz, CDCl3) δ 4.86 (2 H, s), 8.36 (1 H, d, J=4.35 Hz), 8.51 (1 H, d, J=2.56 Hz); MS (ES+): m/z 144.93 (100) [MH+]; HPLC: tR=1.60 min (OpenLynx, polar—7 min).

1. temperatureafter which the reaction was again cooled to −78° C
2. customto react at −78° C. to −70° C. for 10 min
3. temperatureThe temperature was maintained at −78° C. to −70° C. for 2 h
4. customThe reaction was quenched with MeOH (400 mL) at −78° C.
5. customThe solvent was partially removed in vacuo and additional CH2Cl2 (200 mL)
6. additionwas added to the oil
7. customthe reaction mixture was quenched with 2N HCl (900 mL) to a neutral pH
8. extractionThe aqueous layer was extracted with CH2Cl2 (4×) and EtOAc (2×)
9. dry with materialdried over Na2SO4
10. filtrationfiltered
11. concentrationconcentrated in vacuo
12. customgiving a crude black liquid
13. custompurified by chromatography on silica gel [2 kg silica gel, eluting with MeCN:CH2Cl2 2%→5%→10%]