Methyl 4-hydroxy-3-[(trimethylsilyl)ethynyl]benzoate → Methyl 2-trimethylsilylbenzofuran-5-carboxylate

Participants

Reaction Conditions

Reaction Steps

Methyl 4-hydroxy-3-[(trimethylsilyl)ethynyl]benzoate (11 g, 44.5 mmol) is combined with CuI (423 mg, 2.2 mmol) and DIA (7.1 ml, 50 mmol) in MeOH (110 mL) in a flask under nitrogen. The reaction is warmed to 60° C. for 6 h, the volatiles are removed in vacuo, and the brown-green residue is chromatographed over 500 g silica gel (230-400 mesh) eluting with 20% EtOAc/hexane. Two pools are isolated to provide 3.43 g (31%) of the early eluting methyl 2-trimethylsilylbenzofuran-5-carboxylate and 2.63 g (33%) of the later eluting methyl benzofuran-5-carboxylate. The pools are combined in MeOH (130 mL). The solution is treated with 2N NaOH (46.8 ml, 93.6 mmol), is warmed to 50° C., and is stirred for 2 h. The mixture is cooled, the volatiles are removed in vacuo, and the residue is dissolved in water (50 mL). The pH of the mixture is adjusted to 2 with 12N HCl, is diluted with water (40 mL), and the mixture is cooled to 0° C. The off-white solid is collected, washed with water, and is dried to give 6.0 g. The solid is dried in vacuo over P2O5 for 18 h to give 4.6 g (99%) of benzofuran-5-carboxylic acid as an off-white solid. MS for C9H6O3, (EI) m/z: 162 (M)+.

Provenance & Evidence