Hydrochloric Acid → 2,4-Bis(trifluoromethyl)benzaldehyde

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Reaction Steps

A solution of y mol of 2,2,6,6-tetramethylpiperidine in 400 ml of anhydrous tetrahydrofuran is cooled under a stream of argon to to and there is added dropwise thereto at this temperature within 30 minutes 100·y/0.16 ml of a 1.6M solution of n-butyllithium in hexane. Subsequently, 20.2 ml (0.13 mol) of 1,3-bis(trifluoromethyl)benzene are added dropwise thereto at to within 15 minutes, the wine-red solution obtained is stirred for a further×minutes at to and then at this temperature 20 ml (0.26 mol) of N,N-dimethylformamide are allowed to flow in rapidly from a dropping funnel. The internal temperature t rises by about 15° as a consequence of the exothermic reaction. The dark red solution obtained is then slowly added dropwise and while stirring and cooling to 500 ml of cold 3M hydrochloric acid (strongly exothermic). The emulsion obtained is diluted with 300 ml of hexane, the aqueous phase is separated, the organic phase is extracted with 500 ml of cold 3M hydrochloric acid, washed neutral twice with 250 ml of saturated sodium chloride solution each time, dried over sodium sulphate and the organic solvent is largely distilled off at 40° bath temperature/20 kPa. The residue is distilled over a column having a length of 20 cm, whereby firstly residual solvent is removed at 50° bath temperature/20 kPa and then the bath temperature is increased to 80° and the vacuum is increased to 1.4 kPa. During the increase in the internal temperature a forerun of about 1 g is removed and then the 2,4-bis(trifluoromethyl)benzaldehyde obtained distils over at 56°./1.4 kPa as a colourless liquid.

Provenance & Evidence