Triphenylphosphine → 4-(5-Chloro-2-ethoxycarbonyl-3-methyl-benzofuran-6-yloxy)-piperidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

The above prepared 5-chloro-6-hydroxy-3-methyl-benzofuran-2-carboxylic acid ethyl ester (0.900 g, 3.53 mmol) was dissolved in 15 mL of THF and treated successively at −10° C. with 4-hydroxy-piperidine-1-carboxylic acid tert-butyl ester (0.996 g, 1.4 eq.), triphenylphosphine (1.298 g, 1.4 eq.) and DIAD (0.971 mL, 1.4 eq.), and the mixture then kept at ambient temperature for another 3 h. Pouring onto crashed ice/NH4Cl, 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), gave 1.459 g of the title compound as colorless gum.

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