Abstract: The present invention discloses a process for preparing optically pure (R)-4-n-propyl-dihydrofuran-2(3H)-one, belonging to the field of chemical synthesis. According to the process, optically pure (S)-3-n-pentanoyl-4-substituted oxazol-2-one is used as a starting material, and after alkylation, reduction, cyano hydrolysis, lactonization, the product optically pure (R)-4-n-propyl-dihydrofuran-2(3H)-one is given. The preparation process has the advantages of easy availability of raw materials, low price, high yield, high optical purity of product, simple reaction conditions and simple operations.

Abstract: The present invention discloses a novel process for preparing Brivaracetam, belonging to the field of chemical synthesis. According to the process, optically pure (R)-4-n-propyl-dihydrofuran-2(3H)-one was used as a starting material, after the steps of ring opening, halogenation, condensation, ring-closing, etc, high-purity Brivaracetam is given. The preparation process has the advantages of easy availability of raw materials, low price, high yield, high optical purity of product, simple reaction conditions and simple operations.

Abstract: The present invention discloses a process for preparing optically pure (R)-4-n-propyl-dihydrofuran-2(3H)-one, belonging to the field of chemical synthesis. According to the process, optically pure (S)-3-n-pentanoyl-4-substituted oxazol-2-one is used as a starting material, and after alkylation, reduction, cyano hydrolysis, lactonization, the product optically pure (R)-4-n-propyl-dihydrofuran-2(3H)-one is given. The preparation process has the advantages of easy availability of raw materials, low price, high yield, high optical purity of product, simple reaction conditions and simple operations.