Preparation method of isonicotinic acid derivative

The invention provides a preparation method of an isonicotinic acid derivative, which comprises the following steps: (1) reacting a compound as shown in a formula I with di-tert-butyl dicarbonate ester in a solvent in the presence of lithium diisopropylamide to obtain a compound as shown in a formula II; (2) reacting the compound as shown in the formula II with trifluoroacetic acid and triethyl silane in a solvent to obtain a compound as shown in a formula III, namely the isonicotinic acid derivative; compared with a traditional mode of directly introducing carbon dioxide and directly adding dry ice, the method for synthesizing the isonicotinic acid derivative provided by the invention has the advantages that almost no by-product is generated, and the method is simple to operate and treat, relatively low in experimental condition requirement, relatively low in reagent raw material cost, green and environment-friendly, and is suitable for industrial production. The concept of modern organic chemistry developme