C(=O)([O-])[O-].[K+].[K+].CC1C=C(C)C=C(C)C=1S([O-])(=O)=O.[NH2:20][N+:21]1[CH:26]=[C:25]([Cl:27])[N:24]=[C:23]([O:28][CH2:29][C:30]2[CH:35]=[CH:34][CH:33]=[CH:32][CH:31]=2)[CH:22]=1.[C:36]([O:40][CH3:41])(=[O:39])[C:37]#[CH:38].O>CN(C=O)C>[CH2:29]([O:28][C:23]1[C:22]2[N:21]([N:20]=[CH:38][C:37]=2[C:36]([O:40][CH3:41])=[O:39])[CH:26]=[C:25]([Cl:27])[N:24]=1)[C:30]1[CH:31]=[CH:32][CH:33]=[CH:34][CH:35]=1
Potassium carbonate (457 mg, 3.31 mmol) was added to a mixture of 1-amino-3-(benzyloxy)-5-chloropyrazin-1-ium 2,4,6-trimethylbenzenesulfonate 5.34 (992 mg, 2.28 mmol) and methyl propiolate (0.24 mL, 2.66 mmol) in DMF (11 mL) at room temperature. After stifling overnight, reaction mixture was poured into water and extracted with ethyl acetate. Combined organics were washed with 50% brine, dried, filtered, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (0-30% ethyl acetate/hexanes) to yield methyl 4-(benzyloxy)-6-chloropyrazolo[1,5-a]pyrazine-3-carboxylate 5.35 (320 mg).
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