1: With tert.-butyl lithium; potassium hydride in diethyl ether T=0°C; Metallation; 0.833333 h; 2: With tributoxyborane in diethyl ether T=0 - 20°C; boronation; 3: With phosphoric acid in diethyl ether T=0°C; Hydrolysis; 0.5 h;

1: 4-bromo-1H-indole With sodium hydride in diethyl ether T=0°C; 0.5 h; 2: With n-butyllithium in diethyl ether; hexane 0.5 h; Cooling with acetone-dry ice; 3: boric acid trimethyl ester With phosphoric acid; water more than 3 stages;

hydrogenchloride; tert.-butyl lithium in tetrahydrofuran; hexane

1.1: thallium(III) trifluoroacetate / trifluoroacetic acid / 2 h / 20 °C 1.2: 63 percent / CuBr2 / dimethylformamide / 1 h / 120 °C 2.1: 69.1 percent / aq. NaOH / methanol / 1.5 h / Heating 3.1: KH; t-BuLi / diethyl ether; hexane / 0.33 h / -78 °C 3.2: B(n-BuO)3 / diethyl ether; hexane / -78 - 20 °C 3.3: 88 percent / aq. H3PO4 / diethyl ether; hexane / 0 - 20 °C View Scheme

1.1: 69.1 percent / aq. NaOH / methanol / 1.5 h / Heating 2.1: KH; t-BuLi / diethyl ether; hexane / 0.33 h / -78 °C 2.2: B(n-BuO)3 / diethyl ether; hexane / -78 - 20 °C 2.3: 88 percent / aq. H3PO4 / diethyl ether; hexane / 0 - 20 °C View Scheme

1: 3-chloro-pyridine-2,5-dicarboxylic acid dimethyl ester With tetrakis(triphenylphosphine) palladium(0) in toluene T=20°C; Suzuki coupling; 1 h; 2: 1H-indol-4-ylboronic acid With sodium carbonate in ethanol; toluene T=105°C; Suzuki coupling; 8 h; 3: ethanol With hydrogenchloride in diethyl ether T=20°C;

1.1: Pd(PPh3)4 / toluene / 1 h / 20 °C 1.2: aq. Na2CO3 / toluene; ethanol / 8 h / 105 °C 1.3: 91 percent / HCl / diethyl ether / 20 °C 2.1: 85 percent / Ca(BH4)2 / ethanol / 2 h / 20 °C 3.1: 92 percent / MnO2 / CH2Cl2 / 2 h / 20 °C View Scheme