Phosphorus oxychloride → Methyl 2-chlorothieno[2,3-b]pyrazine-6-carboxylate

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Reaction Steps

A solution of methyl 2-oxo-1,2-dihydrothieno[3,2-b]pyrazine-6-carboxylate 21 (0.35 g, 1.665 mmol) in phosphorus oxychloride (10 mL, 107 mmol) was stirred at 105° C. for 5 h. Evaporated to dryness. Dissolved in EtOAc and washed with NaHCO3 solution, brine, dried and evaporated to give crude methyl 2-chlorothieno[3,2-b]pyrazine-6-carboxylate 22 (299 mg, 79%). NMR (400 MHz, CDCl3) 4.02 (s, 3H), 8.11 (s, 1H), 8.61 (s, 1H). (m/z)=229 and 231 (M+H)+.

Provenance & Evidence