Triphenylphosphine → 2-oxo-2H-1-benzopyran-7-yl 4-methoxycarbonyloxybenzoate

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Reaction Steps

13.4 g triphenylphosphine is added to a solution of 8.3 g 7-hydroxycoumarin, 10.0 g 4-methoxycarbonyloxybenzoic acid, 8.9 g diethyl azodicarboxylate and 50 ml tetrahydrofuran at 0° C. The reaction mixture was stirred overnight at room temperature, filtered to remove inorganic material and the filtrate evaporated down, taken up in warm hexane, filtered to remove inorganic material and evaporated down again. The residue is purified by column chromatography on silica gel using hexane/ethyl acetate (1/1 v/v) as eluent and recrystallisation from acetonitrile to yield 12.2 g of 2-oxo-2H-1-benzopyran-7-yl 4-methoxycarbonyloxybenzoate.

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