Intermediate compounds used for preparing brivaracetam, preparation methods for intermediate compounds, and use

A method for preparing Brivaracetam, comprising the following steps:

• (1) preparing an intermediate compound of Formula II:
• reacting a compound of a structural formula of Formula I with an unsaturated hydrocarbon metallic reagent, to obtain the intermediate compound of Formula II, wherein a reaction route is as follows:
• wherein R1 is vinyl or ethynyl;
• (2) preparing a compound with a structural formula of Formula III:
• subjecting the intermediate compound of Formula II to deesterification reaction to obtain the compound with the structural formula of Formula III, wherein a reaction route is as follows:
• (3) preparing a compound with a structural formula of Formula IV:
• subjecting the compound with the structural formula of Formula III to hydrogenation reduction reaction to obtain the compound with the structural formula of Formula IV, wherein a reaction route is as follows:
• (4) preparing Brivaracetam:
• reacting the compound with the structural formula of Formula IV with(S)-2-aminobutanamide in toluene with p-toluenesulfonic acid acting as a catalyst to obtain Brivaracetam, then performing crystallization for purification, wherein a solvent used in the crystallization is a mixture of an ester solvent and an ether solvent, in which the volume ratio of the ester solvent to the ether solvent is 1:(4-6);
• wherein a synthetic route is as follows:
• wherein the molar ratio of the compound with the structural formula of Formula IV to (S)-2-aminobutanamide is 1:(1.0-1.5);
• the reaction temperature is 90-110° C.