反应详情

In a process for preparing dihydro-1H-pyrrolizine-3,5(2H, 6H)-dione comprising the steps of catalytically hydrogenating an ester of 4-(hydroxyimino)heptanedioic acid and subsequently cyclizing the resulting product to dihydro-1H-pyrrolizine-3,5(2H,6H)-dione, the improvement comprises reacting an alcoholic solution of a mono(lower alkyl) ester of 4-(hydroxyimino)heptanedioic acid, wherein lower alkyl comprises from one to three carbon atoms, with hydrogen gas at a temperature of about 60° C. in the presence of rhodium/alumina catalyst and a tertiary lower alkyl amine, wherein said lower alkyl amine comprises from three to nine carbon atoms, to produce 5-oxo-2-pyrrolidinepropanoic acid; and thereafter heating said 5-oxo-2-pyrrolidinepropanoic acid in the presence of a cyclizing agent selected from acetic anhydride, 2,2,6-trimethyl-1,3-dioxen-4-one, and diketene at a temperature of about 90° C. to produce dihydro-1H-pyrrolizine-3,5(2H,6H)-dione.