General procedure for the synthesis of 2-hydroxy-2-cyclopenten-1-one from cis-1,2-cyclopentanediol: cis-1,2-cyclopentanediol (0.424 mmol), Pt/C catalyst (1 or 5 mol% metal loading with respect to the diol), LiOH-H2O (1.0 equiv, 0.424 mmol) and solvent (2 mL, MeCN/H2O 1:1) were added to a 10 mL glass reactor equipped with a condenser and stirred at 60 °C for an appropriate time. The reaction progress was monitored by TLC. When product formation stopped, the catalyst was removed by filtration and washed with EtOAc (3 × 3 mL) to obtain a two-phase solution. The aqueous phase was acidified to pH 5 with 1 M HCl and the layers were separated. The aqueous layer was extracted twice with EtOAc (20 mL). All organic phases were combined, dried with MgSO4 and concentrated in vacuum. The crude product was purified by column chromatography (EtOAc/petroleum ether or MeOH/CH2Cl2) to afford the target product 2-hydroxy-2-cyclopenten-1-one, which is a keto-enol interconjugate isomer.
