Tetrahydrofuran → Methyl 2,2-diethyl-2,3-dihydro-7-methoxybenzofuran-4-carboxylate

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Reaction Steps

10 of methyltriphenylphosphonium bromide-sodium amide mixture (FLUKA 69500) are added to 100 ml of abs. THF at about 10° C. under protective gas (nitrogen), and the mixture is warmed to RT and stirred for about 30 min. A solution of 5.3 g of methyl 4-methoxy-3-(1-methyl-2-oxobutoxy)benzoate is then added dropwise. The mixture is stirred at RT for 1 h, then poured onto water and extracted 3 times with about 50 ml of ethyl acetate. The combined extracts are dried over sodium sulfate and concentrated, and the oily residue is dried in a high vacuum. The oil obtained (3.8 g) is stirred at 190-200° C. for 1 h, cooled and dissolved in 100 ml of toluene. The solution is treated with 5 g of Amberlyst 15 and vigorously stirred at 80° C. overnight. The Amberlyst is then filtered off, the solution is concentrated and the residue is chromatographed on a silica gel column using ethyl acetate/petroleum ether 4:6. The chromatographically pure fractions are combined and concentrated, and the residue is dried in a high vacuum. 1.5 g of the title compound are obtained as a pale yellow oil.

Provenance & Evidence