反应详情

2,2,6,6-Tetramethylpiperidine (20.3 mL, 117 mmol) was added to a solution of n-butyllithium (2.5 M in hexanes, 46 mL, 115 mmol) in dry tetrahydrofuran (1.1 L) at −30° C. The mixture was warmed to room temperature and stirred for 15 minutes. After cooling to −78° C. 2-chloro-6-(3,5-dimethyl-pyrazol-1-yl)-pyrazine (20 g, 96 mmol) in dry tetrahydrofuran (15 mL) was added and the mixture was stirred at −78° C. for 1 h. Ethylformate (12 mL, 143 mmol) was added and the mixture stirred for an additional 2 hours at −78° C. The reaction was quenched with aqueous ammonium chloride, warmed to room temperature and diluted with ethyl acetate. The layers were separated and the aqueous phase was extracted with ethyl acetate. The combined organic layers were washed with brine and dried over sodium sulphate, filtrated and evaporated to give the crude product as a yellow solid. The crude products were purified by flash chromatography (ethyl acetate/heptane as eluent) to give 3-chloro-5-(3,5-dimethyl-pyrazol-1-yl)-pyrazine-2-carbaldehyde (2.9 g, 13%) as a yellow solid and 5-chloro-3-(3,5-dimethyl-pyrazol-1-yl)-pyrazine-2-carbaldehyde (700 mg, 3%) as a yellow solid.

1. temperatureAfter cooling to −78° C
2. stirringthe mixture was stirred at −78° C. for 1 h
3. stirringthe mixture stirred for an additional 2 hours at −78° C
4. customThe reaction was quenched with aqueous ammonium chloride
5. temperaturewarmed to room temperature
6. additiondiluted with ethyl acetate
7. customThe layers were separated
8. extractionthe aqueous phase was extracted with ethyl acetate
9. washThe combined organic layers were washed with brine
10. dry with materialdried over sodium sulphate
11. filtrationfiltrated
12. customevaporated
13. customto give the crude product as a yellow solid
14. customThe crude products were purified by flash chromatography (ethyl acetate/heptane as eluent)