Preparation method of N-alkyl-2-fluoroaniline

The invention provides a preparation method of N-alkyl-2-fluoroaniline, which comprises the following steps: S1) in the presence of an acid catalyst, carrying out heating reaction on o-fluoroaniline and trialkyl orthoformate to obtain an acylated intermediate product; and (S2) hydrolyzing the acylated intermediate product, so as to obtain the N-alkyl-2-fluoroaniline. Compared with the prior art, the method has the advantages that the o-fluoroaniline is used as the raw material, the trialkyl orthoformate is used as the acylation reagent, the acylated intermediate product is prepared through a substitution-rearrangement one-pot method under the action of the catalyst, then the N-alkyl-2-fluoroaniline is obtained through hydrolysis, the raw materials are cheap and easy to obtain, the process route is short, harsh reaction conditions are not contained, operation is safe, and the method is suitable for industrial production. The method has the advantages of high conversion rate, less organic solvent, effective red