Synthetic method for o-cyclodione

The invention discloses a synthetic method for o-cyclodione. O-cyclodione normally comprises 1,2-cyclopentanedione, 3-methyl-1,2-cyclopentanedione (methyl cyclopentenolone), 1,2-cyclohexanedione, 1,2-cyclononanedione, etc. 3-methyl-1,2-cyclopentanedione is an important perfume, and 1,2-cyclohexanedione is an important raw material for production of the perfume 5,6,7,8-tetrahydroquinoxaline. According to the invention, cyclic ketone is used as a starting raw material and subjected to nitrosation with nitrite, and an obtained intermediate cyclic ketoxime is subjected to hydrolysis so as to obtain o-cyclodione. The synthetic method provided by the invention has the advantages of simple technological operation, little pollution to the environment, high reaction yield and low production cost and is a promising production process.