Reactions of enol ethers of cyclopentane-1, 3-dione derivatives (I) with cyanide ion were investigated in order to develope new synthetic routes to 3-functionalized-2-cyclopenten-l-one derivatives from I. I could be converted to the 3-cyano-2-cyclopenten-1-one skeleton by several procedures for hydrocyanation, among which Nagata's reagents (HCN-triethylaluminium, 6) diethyl-aluminium cyanide8) were proved to be potent ones. Reactions of enol ethers of 4-hydroxy-cyclopentane-1, 3-dione derivatives were also in-vestigated. From 4-hydroxy-3-methoxy-2-cyclopenten-1-one derivatives (V) 1, 4-addition type products with the 4-hydroxy-3-cyano-2-cyclopenten-l-one skeleton (VIII) were obtained as sole isolatable products. NMR studies of some hydroxy-cyclopentenone derivatives were also described.