Chlorodifluoromethane → Methyl 9-difluoromethylxanthene-9-carboxylate

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Reaction Steps

16.8 g (0.07 mol) of methyl 9-xanthenecarboxylate (obtainable according to step 1.1.a) are dissolved in 300 mL of tetrahydrofuran and 9.1 g (0.077 mol) of potassium tert-butoxide are added batchwise while cooling. Then difluorochloromethane is piped in at 0° C. over a period of 1.5 hours. After all the gas has been piped in, the reaction mixture is left to stand for 72 hours at ambient temperature. The reaction mixture is then diluted with water to a total volume of about 2000 mL, extracted with ethyl acetate, the organic phase is separated off and washed with 5% aqueous sodium carbonate solution. After being extracted again with water, the organic phase is dried over magnesium sulfate and the solvent is removed by distillation. The crude product is purified by chromatography on silica gel (eluent: cyclohexane-ethyl acetate (98:2)) or by recrystallization from cyclohexane. Yield: 5.35 g of white crystals (26% of theoretical yield); melting point: 101° C.

Provenance & Evidence