Multi-step reaction with 4 steps 1: caesium carbonate; palladium diacetate; dicyclohexyl(2′,6′-dimethoxybiphenyl-2-yl)phosphine / toluene / 40 h / |Reflux2: palladium diacetate; potassium carbonate; 2,2,2-trimethylacetic acid / 14 h / 115 °C3: potassium phosphate; pyrrole-2-carboxylic acid ester / dimethyl sulfoxide / 40 h / 110 °C4: diisobutylaluminium hydride / diethyl ether / 4 h / -78 °C