Triphenylphosphine → (S)-2-[4-(5-Trifluoromethyl-pyridin-2-yloxy)-phenoxy]-propionic acid benzyl ester

Beteiligte Stoffe

Reaktionsschritte

To a solution of 4-(5-trifluoromethyl-pyridin-2-yloxy)-phenol (2.90 g, 11.4 mmol) and (R)-2-hydroxypropionic acid benzyl ester (2.25 g, 12.5 mmol) in dry THF (100 mls) at 0° C. under nitrogen is added triphenylphosphine followed by dropwise addition of diisopropylazodicarboxylate (3.36 mls, 17 mmol). The resulting yellow mixture is stirred for 1 hr then left the stand for 16 hours. The reaction mixture is partitioned between water and ethyl acetate and the layers separated. The aqueous is further extracted with ethyl acetate and the combined organic layers dried over magnesium sulphate, filtered and the solvent removed under reduced pressure. Column chromatography on silica gel using 10% ethyl acetate/hexane as eluent yielded (S)-2-[4-(5-Trifluoromethyl-pyridin-2-yloxy)-phenoxy]-propionic acid benzyl ester as a colourless oil. In one example 3.25 g are made representing 69% yield and in >99% ee (as determined by nmr).

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