How is 5-fluoro-2-methyl-1H-indole-3-carbaldehyde (CAS: 815586-68-6) typically synthesized?

5-fluoro-2-methyl-1H-indole-3-carbaldehyde can be synthesized through the aromatic substitution of 2-methyl-1H-indole-3-carbaldehyde with fluorine using fluorine gas in the presence of an iron catalyst. The reaction is carried out under anhydrous conditions to ensure high yield and selectivity. The use of fluoride salts or fluorine gas is common, with the goal of achieving a high level of product purity and yield.