1: methyl 1H-indole-4-carboxylate With sodium hydride in N,N-dimethyl-formamide; mineral oil T=20°C; Inert atmosphere; 2: methyl iodide in N,N-dimethyl-formamide; mineral oil T=20°C; 16 h; Product distribution / selectivity;

1: 1H-indole-4-carboxylic acid With sodium hydride in N,N-dimethyl-formamide T=20°C; Metallation; 1 h; 2: methyl iodide in N,N-dimethyl-formamide T=20°C; Alkylation; 5 h;

sodium hydroxide in methanol; water 8 h; Heating;

1: N,N-dimethyl-formamide With trichlorophosphate T=0°C; Vilsmeier Formylation; Cooling with ice; 2: methyl 1-methyl-1H-indole-4-carboxylate Vilsmeier Formylation; 6 h; 3: With sodium hydroxide in water Vilsmeier Formylation; pH=7; Cooling with ice;

1: NaOH / methanol; H2O / 8 h / Heating 2: triethylamine; diphenylphosphorazidate / benzene / 1 h / 20 °C 3: toluene / 1 h / Heating View Scheme