Triphenylphosphine → 4-(2-Ethoxycarbonyl-benzo[b]thiophen-6-yloxy)-piperidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

The above prepared 6-hydroxy-benzo[b]thiophene-2-carboxylic acid ethyl ester (0.206 g, 0.927 mmol, see example 7, step 1 and 2) was dissolved in 5 mL of THF and treated successively at −10° C. with 4-hydroxy-piperidine-1-carboxylic acid tert-butyl ester (0.261 g, 1.4 eq.), triphenylphosphine (0.340 g, 1.4 eq.) and DIAD (0.255 mL, 2 eq.), and the mixture then kept at ambient temperature over night. Pouring onto crashed ice, twofold extraction with AcOEt, washing with water and brine, drying over magnesium sulfate, and evaporation of the solvents, followed by flash chromatography (SiO2, hexane AcOEt=85/15), yielded 0.355 g of the title compound as colorless gum.

Provenance & Evidence