Phosphorus oxychloride → Methyl 5-chloro-3-methylpyrazine-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

In a 1-L flask, the crude 3-(methoxycarbonyl)-2-methylpyrazine 1-oxide (step 2, 17.77 g, 106 mmol) was dissolved in DMF (300 mL). Neat phosphoryl trichloride (29.6 mL, 317 mmol) was added. The reaction mixture was heated to 100° C. After 1 h, the reaction mixture was concentrated to remove most of the DMF. The flask was cooled in an ice water bath, and 1 M aqueous Na2CO3 (300 mL) was added slowly, followed by 80% EtOAc-hexane (400 mL). The mixture was filtered through Celite. The resulting filtrate was partitioned and the aqueous phase was extracted further with 80% EtOAc-hexane (2×250 mL). The combined organic layers were dried over MgSO4 and concentrated. The material was purified through silica gel using 11% EtOAc-hexane to afford the title compound (4.29 g, 23 mmol, 22%). MS m/z=187 [M+H]+. Calculated for C7H7ClN2O2: 186. 1H NMR in CDCl3 δ: 8.51 (s, 1H), 4.01 (s, 3H), 2.86 (s, 3H).

Provenance & Evidence