Entry Pd Source Solvent Base Yield (%)b 1 2 1 Pd(OAc)2 DMA / 0.5 M H2O K2CO3 tracec 56 2 Pd(OAc)2 DMF / 0.5 M H2O K2CO3 7 62 3 Pd(OAc)2 DMA / 5 M H2O K2CO3 19 26 4 Pd(OAc)2 DMF / 5 M H2O K2CO3 34 0 5 Pd(OAc)2 DMF / 2 M H2O K2CO3 24 10 6 Pd(OAc)2 CH3CN / 5 M H2O K2CO3 15 21 7 Pd(Ph3P)2Cl2 DMF / 5 M H2O K2CO3 tracec 0 8 Pd(dppf)2Cl2·CH2Cl2 DMF / 5 M H2O K2CO3 tracec 0 9 Pd(MeCN)2Cl2 DMF / 5 M H2O K2CO3 46 0 10 Pd(PhCN)2Cl2 DMF / 5 M H2O K2CO3 52 0 11 Pd(PhCN)2Cl2 DMF / 0.5 M H2O K2CO3 8 79 12 Pd(PhCN)2Cl2 DMF / 0.5 M H2O KHCO3 tracec 67 13 Pd(PhCN)2Cl2 DMF / 0.5 M H2O NaHCO3 85 7 14 Pd(PhCN)2Cl2 DMF / 0.5 M H2O KOAc 58 0 15 Pd(PhCN)2Cl2 DMF / 0.5 M H2O NaOAc 42 0 aGeneral reaction conditions: Pd (0.171 mmol), indole (1.71 mmol), norbornene (3.41 mmol), base (6.84 mmol), ethyl bromoacetate (3.41 mmol), solvent (8 mL, total), 70°C, 14 h. bIsolated yield. cMonitored by LC-MS and TLC

Table 1: Optimization of the catalysis conditionsa.