Triethylamine → 7-[5-Formyl-2-trifluoromethoxy-phenyl]-3,3-dimethyl-2,3-dihydro-benzofuran-5-carboxylic acid dimethylamide

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To a solution of 7-bromo-3,3-dimethyl-2,3-dihydro-benzofuran-5-carboxylic acid dimethylamide (437 mg, 1.46 mmol) in dioxane (4 mL), were added under argon, triethylamine (0.82 mL, 5.86 mmol), Pd(OAc)2 (16 mg, 0.07 mmol), 2-(dicyclohexylphosphino)biphenyl (103 mg, 0.29 mmol) and pinacolborane (0.64 mL, 4.40 mmol) dropwise. The mixture was heated at 80° C. under argon for 2 hrs then cooled to room temperature. Water (0.5 mL) was added dropwise, then Ba(OH)2.8H2O (1.38 g, 4.40 mmol) followed by 3-bromo-4-trifluoromethoxy benzaldehyde (473 mg, 1.76 mmol) dissolved in dioxane (1.2 mL). The mixture was refluxed for 4 hours then cooled to room temperature, diluted with ethyl acetate and filtered over celite. The solution was further washed with water and brine, dried over anhydrous magnesium sulfate, filtered and evaporated. The residue was purified on silica gel (5% methanol in dichloromethane) to give 264 mg of 7-[5-formyl-2-trifluoromethoxy-phenyl]-3,3-dimethyl-2,3-dihydro-benzofuran-5-carboxylic acid dimethylamide (containing 50% of 3,3-dimethyl-2,3-dihydro-benzofuran-5-carboxylic acid dimethylamide as determined by 1H NMR) use as this in the next step.

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