Nitrogen gas was bubbled through a mixture of 1.4 g (5.25 mmol) of ethyl 3-bromo-4-chloro-5-methyl-1H-pyrrole-2-carboxylate (Intermediate 14), 470 g (4 mol) Zn(CN)2, 250 mg (0.26 mmol) Pd2(dba)3 and 302 mg (0.26 mmol) dppf in 15 ml DMF for 15 min. The mixture was heated at 130° C. for 1 h. Additional Zn(CN)2 (1 g), Pd2(dba)3 (500 mg) and dppf (604 mg) were added. After bubbling through N2 for 15 min and heating at 130° C. for 2 h, additional Zn(CN)2 (0.5 g), Pd2(dba)3 (250 mg) and dppf (302 mg) were added. Heating was continued at 130° C. for 2 h. Solvent was removed and the residue was partitioned between EtOAc and water. The EtOAc was separated and washed with brine. Combined aqueous layers were extracted again with EtOAc, which was washed with brine. Combined EtOAc extracts were dried (MgSO4) and concentrated. The residue was purified by silica gel chromatography (100% CH2Cl2 followed by gradient elution to 5% MeOH in CH2Cl2) to afford 750 mg of product as a solid. MS (ES) (MH+): 213 for C9H9ClN2O2; NMR (d6-DMSO): 1.3 (t, 3H), 2.2 (s, 3H), 4.3 (q, 2H), 13.1 (s, 1H).
