Trifluoroacetic acid → (1S,2S)-2-(4-Hydroxy-phenyl)-cyclopropanecarboxylic acid ethyl ester

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Reaction Steps

(1S,2S)-2-(4-tert-Butoxy-phenyl)-cyclopropanecarboxylic acid ethyl ester (10.5 g, 35.6 mmol) is dissolved in trifluoroacetic acid (15 mL, 196 mmol) and stirred for 5 minutes. The mixture is concentrated under vacuum, then re-evaporated five times from dichloromethane. The residue is dissolved in boiling cyclohexane (20 mL) and then allowed to cool. The cyclohexane layer is decanted off and the operation repeated. The residue is dried under vacuum to give the title compound (yield 6.51 g). GC (METHOD 1): tR=11.04 min; Mass spectrum (EI+): m/z=206 [M]+, e.e. 96% by chiral HPLC (Column: Daicel Chiralpak AS-H, 4.6×250 mm, 5 μm Mobile phase: hexane:ethanol 95:5, 1 mL/min, 25° C.) tR=14.17 (13.11) min.

Provenance & Evidence