Phosphorus oxychloride → 3,6-Dichloropyrido[2,3-b]pyrazine

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Reaction Steps

6-chloropyrido[3,2-b]pyrazin-3(4H)-one (E-27) (9 g, 49.8 mmol) was dissolved in POCl3 (100 mL) and the resulting mixture was stirred at reflux for 3 h. The reaction was complete based on TLC analysis. The mixture was cooled to RT and concentrated in vacuo to remove POCl3. The residue was poured into ice water (150 mL) and extracted with DCM (3×100 mL). The combined organic layers were washed with brine, dried over Na2SO4 and filtered. The filtrate was concentrated in vacuo to give the desired product 3,6-dichloropyrido[2,3-b]pyrazine (E-28) (9 g, 90% yield) as a solid. ESI-MS m/z: 199.97 [M+H]+.

Provenance & Evidence