Triethylamine → methyl 6-cyclohexyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4H-thieno[3,2-b]pyrrole-2-carboxylate

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Reaction Steps

To a solution of methyl 5-bromo-6-cyclohexyl-4H-thieno[3,2-b]pyrrole-2-carboxylate (2.00 g, 5.84 mmol) in 1,4-dioxane (20 ml) was added triethylamine (3.20 ml, 22.9 mmol). 4,4,5,5-Tetramethyl-1,3,2-dioxaborolane (2.50 ml, 17.2 mmol) was added dropwise under an argon stream and the mixture was stirred at room temperature for 30 min. To the mixture were added 2-(dicyclohexylphosphino)biphenyl (245 mg, 0.699 mmol) and palladium acetate(II) (39.0 mg, 0.173 mmol) under an argon stream, and the mixture was stirred at 100° C. for 2 hr. The reaction mixture was allowed to cool to room temperature, and saturated aqueous ammonium chloride solution was added. The mixture was extracted with ethyl acetate, and the organic layer was washed with water and saturated brine in this order, and dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure. A mixed solvent of hexane-ethyl acetate (10:1) was added to the obtained residue and the precipitated solid was collected by filtration. The obtained solid was dried under reduced pressure to give methyl 6-cyclohexyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4H-thieno[3,2-b]pyrrole-2-carboxylate (1.66 g, yield 74%).

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