[N:1]([CH2:4][CH2:5][N:6]1[CH:10]=[C:9]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH:8]=[C:7]1[C:16]([O:18]CC)=O)=[N+]=[N-].C(=O)([O-])[O-].[K+].[K+]>CCO.[Pd]>[O:18]=[C:16]1[NH:1][CH2:4][CH2:5][N:6]2[CH:10]=[C:9]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH:8]=[C:7]12To a solution of diethyl 1-(2-azidoethyl)-1H-pyrrole-2,4-dicarboxylate (10 g, 35.68 mmol) in EtOH (1000 mL) was added 10% Pd/C (3 g). The resulting residue was stirred at rt under a 30 psi H2 atmosphere for 2 h. The palladium catalyst was filtered. To the filtrate was added potassium carbonate (5 g, 36 mmol) and the mixture was refluxed overnight. All solids were removed by filtration, and the filtrate was concentrated. Purification via flash chromatography (DCM: methanol, 50:1 to 20:1) afforded ethyl 1-oxo-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine-7-carboxylate (2.5 g, 41%). 1H NMR (DMSO-d6, 300 MHz) δ7.91 (s, 1 H), 7.64 (s, 1H), 6.90 (s, 1 H), 4.18 (m, 4 H), 3.50 (m, 2 H), 1.25 (t, J=5.4 Hz, 3 H).
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