(E)-3-(2-(piperidin-1-yl)-6-(trifluoromethyl)pyridin-3-yl)acrylic acid (150.0 mg, 0.50 mmol) was suspended in dry THF (7.0 mL). DMAP (111.4 mg, 0.91 mmol) and caesium carbonate (296.0 mg, 0.91 mmol) were added and the mixture was stirred at rt for 15 minutes. 5,8-Dichloro-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline hydrobromide (143.0 mg, 0.45 mmol), EDC.HCl (130.6 mg, 0.68 mmol), HOBt (69.8 mg, 0.45 mmol) were then added. The mixture was stirred at rt overnight. Water (100 mL) was added and the product extracted with EtOAc. Combined organic extracts were dried (MgSO4), filtered and concentrated. Purification was done first using flash column chromatography (CH2Cl2/MeOH 98/2→95/5) and then by size exclusion (Sephadex LH20; CHCl3/MeOH 1/1) to yield 55.0 mg (24%) of the title product.
