(1-Hydroxymethyl-cyclopentyl)-(4-(4-methylphenyl)piperazin-1-yl)-methanone from the previous step (1.57 g, 5.22 mmol) was dissolved in DCM (40 mL). Dess-Martin periodinane (3.06 g, 7.22 mmol) was added and the reaction mixture was stirred at room temperature for 3.5 hours. The reaction mixture diluted with Et2O (100 mL) and 1M aq NaOH solution (50 mL) was added. The reaction mixture was stirred for 20 minutes and then the organic layer was separated and washed with 1M aq NaOH solution (50 mL), water (50 mL), dried (MgSO4) and concentrated in vacuo to give 1-(4-(4-methylphenyl)-piperazine-1-carbonyl)-cyclopentanecarbaldehyde (1.64 g, 105%) as a brown oil which was used without further purification.
