Br[CH2:2][CH2:3][N:4]1[CH:8]=[C:7]([C:9]([O:11][CH2:12][CH3:13])=[O:10])[CH:6]=[C:5]1[C:14]([O:16][CH2:17][CH3:18])=[O:15].[N-:19]=[N+:20]=[N-:21].[Na+]>CN(C=O)C.O.CCOC(C)=O>[N:19]([CH2:2][CH2:3][N:4]1[CH:8]=[C:7]([C:9]([O:11][CH2:12][CH3:13])=[O:10])[CH:6]=[C:5]1[C:14]([O:16][CH2:17][CH3:18])=[O:15])=[N+:20]=[N-:21]To a solution of diethyl 1-(2-bromoethyl)-1H-pyrrole-2,4-dicarboxylate (0.8 g) in DMF (10 mL) was added sodium azide (0.2 g, 3.07 mmol). The resulting mixture was stirred at rt overnight then diluted with water (10 mL) and EtOAc (100 mL). After separation, the aqueous layer was extracted with EtOAc (2×50 mL). The combined organic layers were washed with brine, dried (MgSO4) and concentrated. Purification via flash chromatography (petroleum ether:EtOAc, 20:1 to 15:1) afforded diethyl 1-(2-azidoethyl)-1H-pyrrole-2,4-dicarboxylate (0.4 g, 57%). 1H NMR (CDCl3, 300 MHz) δ7.49 (d, J=1.8 Hz, 1 H), 7.43 (d, J=1.8 Hz, 1 H), 4.88 (t, J=5.5 Hz, 2 H), 4.32 (q, J=7.2 Hz, 4 H), 3.70 (t, J=6.4 Hz, 2 H), 1.38 (m, 6 H).
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