The present application relates to the preparation method of carboxyl endocyclic anhydride and the preparation product. The preparation method of compound of formula (II) comprises the following steps: reacting compound of formula (I) with a cyclization
reagent to generate compound of formula (II) and acid, and using an
epoxide compound as an acid
scavenger. The present application is a new synthesis method of carboxyl endocyclic anhydride, which has the advantages of low cost, low requirement for reagents, site and equipment, mild conditions, wide substrate application range, high functional group tolerance, recyclable
solvent and other high value-added by-products in the synthesis
route, less waste liquid
discharge, easy scale-up, high industrial and academic value, and the like, and can greatly promote the rapid large-scale production and application of
polyamino acid, polyhydroxy acid (
polyester), polymercaptan acid (polythioester) and the like.