Hydrochloric Acid → 2-(2,2',4'-Trifluoro-4-biphenylyl)propionic acid

Beteiligte Stoffe

Reaktionsschritte

Hydroxylamine sulphate (3.02 g.) was added to an aqueous solution of sodium acetate [prepared from glacial acetic acid (2.4 ml.), 18N aqueous sodium hydroxide (2.34 ml.) and water (23 ml.)]. 2-(2,2',4'-Trifluoro-4-biphenylyl)propionaldehyde (8.26 g.) in ethanol (23 ml.) was added and the mixture was stirred at room temperature for 2.5 hours and then at 90° C. for 1 minute. After cooling, the precipitated oxime was suspended in water containing nickel sulphate (0.2 g.) and heated to reflux to obtain an aqueous suspension of 2-(2,2',4'-trifluoro-4-biphenylyl)propionamide. Aqueous sodium hydroxide (18N, 6.75 ml.) was then added and refluxing continued for 24 hours. The resulting solution was cooled to 40° C., acidified with concentrated hydrochloric acid, and the product isolated in ether. After some purification by a conventional back-extraction technique with aqueous potassium carbonate, the final ether extract was evaporated to dryness. This crude acid in methylene chloride was chromatographed on a column of a synthetic magnesia/silica gel adsorbent. Evaporation of the eluate and recrystallisation of the residue from petroleum ether (b.p. 80°-100° C.) gave 2-(2,2',4'-trifluoro-4-biphenylyl)propionic acid, m.p. 105°-108° C.

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