反応 #53435

反応方程式

TFA

phosphorus oxychloride

ethyl 3-ethoxy-O-ethyl-N-(1H-pyrrol-2-ylmethylene)serinate

NaHCO3

NaHCO3

→

ethyl pyrrolo[1,2-a]pyrazine-3-carboxylate

収率 24.0%

溶媒

1,2-dichloroethane

反応条件

後処理

1. 1
   その他The phases are separated
2. 2
   抽出the basic phase extracted with EtOAc (4×100 mL)
3. 3
   洗浄washed with brine
4. 4
   乾燥dried over Na2SO4
5. 5
   ろ過filtered
6. 6
   濃縮concentrated
7. 7
   その他to give a black oil that
8. 8
   その他is purified with silica gel chromatography (35% EtOAc/heptanes to 50% over several liters)

実験手順

To a hot (65° C.) solution of TFA (44 mL, 510 mmol) and phosphorus oxychloride (39.0 g, 140 mmol) is added drop-wise a solution of ethyl 3-ethoxy-O-ethyl-N-(1H-pyrrol-2-ylmethylene)serinate (Dekhane, M; Potier, P; Dodd, R. H. Tetrahedron, 49, 1993, 8139-46.) (9.6 g, 28.0 mmol) in anhydrous 1,2-dichloroethane (200 mL). The black mixture is allowed to stir at 65° C. for 18 h at which point it is cooled to rt and neutralized with sat. NaHCO3 and solid NaHCO3 to pH ˜9. The phases are separated and the basic phase extracted with EtOAc (4×100 mL). The organic phases are combined, washed with brine, dried over Na2SO4, filtered, and concentrated to give a black oil that is purified with silica gel chromatography (35% EtOAc/heptanes to 50% over several liters) to give a light brown solid for ethyl pyrrolo[1,2-a]pyrazine-3-carboxylate. Yield 24%. HRMS (FAB) calcd for C10H10N2O2+H 191.0820, found 191.0823.

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