[F:1][C:2]1[C:7](I)=[N:6][CH:5]=[CH:4][N:3]=1.[I-].[C:10]([O:14][C:15]([N:17]1[CH2:21][CH2:20][CH:19]([Zn+])[CH2:18]1)=[O:16])([CH3:13])([CH3:12])[CH3:11]>C1(P(C2C=CC=CC=2)[C-]2C=CC=C2)C=CC=CC=1.[C-]1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=C1.[Fe+2].[Cu]I.CC(N(C)C)=O>[F:1][C:2]1[C:7]([CH:20]2[CH2:19][CH2:18][N:17]([C:15]([O:14][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:16])[CH2:21]2)=[N:6][CH:5]=[CH:4][N:3]=1
Into an oven-dried flask were charged 2-fluoro-3-iodopyrazine (3.08 g, 13.8 mmol), 1,1′-bis(diphenylphosphino)ferrocene]dichloride palladium(ii)complex with dichloramethane (0.34 g, 0.41 mmol), copper(i) iodide (0.16 g, 0.83 mmol), and DMA (20 mL). The resulting mixture was degassed with alternating vacuum/nitrogen purges. The (1-(tert-butoxycarbonyl)pyrrolidin-3-yl)zinc(II) iodide (6.98 g, 19.3 mmol) solution from previous step was filtered through a regular filter into the mixture. It was degassed one more time and then heated to 80° C. with stirring for 16 h. After cooling to RT, the reaction mixture was partitioned between EtOAc and 1 N NH4Cl. The aqueous layer was back extracted with EtOAc (2×) and the combined EtOAc layers were washed once again with 1 N NH4Cl, then with brine, dried (Na2SO4) and concentrated. The crude material as chromatographed through a Redi-Sep pre-packed silica gel column (120 g), eluting with a gradient of 0% to 30% EtOAc in hexane, to provide tert-butyl 3-(3-fluoropyrazin-2-yl)pyrrolidine-1-carboxylate as orange oil. MS (ESI, pos. ion) m/z: 212.0 (M−56).
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