Tributyltin Chloride → 3-Tri-n-butylstannylbenzofuran

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A solution of bromine (4.49 g, 28.09 mmol) in chloroform (5 mL), was added slowly to a stirred mixture of benzofuran (1.58 g, 13.38 mmol) and potassium acetate (2.69 g, 27.42 mmol) in chloroform (20 mL) at room temperature. After the addition was complete, the reaction mixture was warmed to 50° C. and stirred at this temperature for 5 h. The solution was then allowed to cool, and washed with 5% NaHSO3, then brine, then dried through MgSO4, filtered and evaporated to give trans-2,3-dihydro-2,3-dibromo-benzofuran as a pale-yellow solid (2.88 g). The pale-yellow solid (2.18 g, 7.84 mmol) was dissolved in anhydrous ethanol (20 mL) then sodium ethoxide (1.33 g, 19.60 mmol) was added and the resulting mixture was heated to 50° C. and stirred at this temperature for 5 h. The solution was allowed to cool, then brine added, and the solution was extracted with ether. The ether layer was washed with water and brine, dried through MgSO4, and the solvent was evaporated to give a brown oily residue. Purification by flash chromatography using a gradient of ammoniated methanol in chloroform gave 3-bromo-benzofuran as a light-brown oil (1.50 g). Under nitrogen, the 3-bromobenzofuran (450 mg, 2.28 mmol) was then dissolved in anhydrous ether, (10 mL) and stirred at −78° C. n-Butyllithium (1.6M, 2.3 mL, 3.65 mmol) was added, and stirring was continued at −78° C. After 15 min, tri-n-butylstannyl chloride (668 mg, 2.05 mmol) was added, then the solution was allowed to warm to room temperature, and stirring was continued for another 1 h. The mixture was quenched, and washed with 1N sodium hydroxide, dried through MgSO4, and then the solvent was evaporated to give a brown oily residue. Purification by flash chromatography using a gradient of ammoniated methanol in chloroform as the eluant gave the sub-title compound as a yellow oil (570 mg).

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