Реакция #164511

Уравнение реакции

dimethylsulfide

dihydropyrazine

(S)-3,6-diethoxy-2-isopropyl-2,5-dihydro-pyrazine

n-butyllithium

cyclohept-2-eneone

→

title compound

Выход 72.0%

3-((2R,5S)-3,6-Diethoxy-5-isopropyl-2,5-dihydro-pyrazin-2-yl)-cycloheptanone

Выход 72.0%

Растворители

tetrahydrofuran

tetrahydrofuran

Условия реакции

Обработка

1. 1
   workup.ADDITIONis added slowly via syringe
2. 2
   Другоеat −50° C
3. 3
   ТемператураThe reaction is warmed to −30° C.
4. 4
   workup.STIRRINGstirred further for 30 minutes
5. 5
   ТемператураThe reaction is then cooled to −78° C.
6. 6
   Другоеquenched by the addition of a saturated aqueous solution of ammonium chloride at −78° C
7. 7
   Температураto warm to ambient temperature
8. 8
   workup.ADDITIONdiluted with water
9. 9
   Экстракцияextracted with diethyl ether
10. 10
    ПромывкаThe organic extracts were washed with ammonium chloride, dilute ammonium hydroxide, water and brine
11. 11
    Сушкаdried over magnesium sulfate
12. 12
    Концентрированиеconcentrated in vacuo
13. 13
    ДругоеThe residue is purified by column chromatography
14. 14
    Промывкаeluting with a gradient of hexane in ether (20-25%)

Методика

A solution of (S)-3,6-diethoxy-2-isopropyl-2,5-dihydro-pyrazine (6.0 g, 28.3 mmol) in tetrahydrofuran (58 mL) is cooled to −78° C. n-butyllithium (1.6 M in hexane, 21.4 mL, 34.2 mmol) is added slowly via syringe, and the reaction is allowed to stir at −78° C. for 30 minutes. The reaction mixture is then transferred via canula to a solution of CuBr-Me2S (3.35 g, 16.3 mmol) in tetrahydrofuran:dimethylsulfide (90 mL, [2:1]) at −50° C. The reaction is warmed to −30° C. and stirred further for 30 minutes. The reaction is then cooled to −78° C. and cyclohept-2-eneone (5.23 mL, 46.9 mmol) is added dropwise over 10 minutes. The reaction is maintained at −78° C. until the disappearance of the dihydropyrazine is confirmed by TLC and quenched by the addition of a saturated aqueous solution of ammonium chloride at −78° C. The reaction is allowed to warm to ambient temperature, diluted with water, and extracted with diethyl ether. The organic extracts were washed with ammonium chloride, dilute ammonium hydroxide, water and brine, dried over magnesium sulfate, and concentrated in vacuo. The residue is purified by column chromatography eluting with a gradient of hexane in ether (20-25%) to afford the title compound (6.52 g, 72% yield), slightly contaminated with cyclohept-2-enone. LCMS (m/z): 323.13 (M+1).

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