A slurry of 2-(4-(1,3-dioxan-2-yl)-2-fluorophenyl)-5-(1-phenylcyclopent-3-enyl)-thiazolo[5,4-b]pyridine (0.550 g, 1.20 mmol) in 8 mL 1:1 THF/5N HCl was heated to 70° C. in a sealed vial. After 30 min, the reaction mixture was cooled, treated with ice, 10N NaOH until basic, and EA. The organic layer was washed with water, brine, dried over sodium sulfate, filtered, and concentrated in vacuo to give 3-fluoro-4-(5-(1-phenylcyclopent-3-enyl)-thiazolo[5,4-b]pyridine-2-yl)benzaldehyde which was used without further purification. MS (ESI) m/z: Calculated: 400.1; Observed: 401.1 (M++1).
