Potassium Bicarbonate → (+/-)-5,10-Dihydro-1-isopropoxy-9-methoxy-10-(2-trifluoromethylphenyl)-pyrido[4,3-b][1,6]naphthyridine

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Reaction Steps

7.5 g (18.7 mMole) (±)-1,2,5,10-tetrahydro-9-isopropoxy-1-oxo-10-(2-trifluoromethylphenyl)-pyrido[4,3-b][1,6]naphthyridine (see Example 2) and 5.0 g (34 mMole) trimethyloxonium tetrafluoroborate are stirred for 24 hours at ambient temperature in 200 ml 1,2-dichloroethane under an atmosphere of nitrogen. The reaction mixture is then shaken with a saturated aqueous solution of potassium hydrogen carbonate and the organic phase is separated off, washed with water and dried over anhydrous sodium sulphate. The residue obtained after evaporation in a vacuum is chromatographed on silica gel with toluene/ethyl acetate (3:1 v/v). The fraction with the Rf of 0.2 is isolated and recrystallized from n-hexane/diisopropyl ether. There is obtained (±)-5,10-dihydro-1-isopropoxy-9-methoxy-10-(2-trifluoromethylphenyl)-pyrido[4,3-b][1,6]naphthyridine in the form of colorless crystals; mp 183°-185° C.

Provenance & Evidence