Cyclic esterketone compounds, processes for the synthesis thereof and process for the preparation of poly (esterketone) polymers

PROBLEM TO BE SOLVED: To provide a monomer compound, which is improved to be useful as the novel monomer for forming a poly(ester ketone)polymer by polymerization, and can be directly synthesized in high yield in a one-stage process from the stock material. SOLUTION: This compound is a novel cyclic ester compound, in particular 2-oxepane-1,5-dione (KCL), synthesized in one-stage process involving oxidation of the stock material (cyclic diketone, e.g. 1,4-cyclohexane-dione) and useful for simply and easily producing a poly(ester ketone)polymer, in particular poly(2- oxepane-1,5-dione) (PKCL) in high yield.