Formaldehyde → 4-fluoro-2-methylene-2,3-dihydro-1H-inden-1-one

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Reaction Steps

To a 1000 mL round bottle flask were charged 4-fluoro-2,3-dihydro-1H-inden-1-one (249a) (5.04 g, 33.6 mmol), paraformaldehyde (10.08 g, 336 mmol), phenylboronic acid (4.92 g, 40.3 mmol) followed by toluene (235 mL), to the suspension was added TFA 2.6 mL, 33.6 mmol), and the resulting suspension was refluxed for 4 hrs, which resulted a clear yellowish solution. The solution was cooled to room temperature, and the pH was adjusted to 7-8 by adding saturated NaHCO3. After extracting with ethyl acetate, the organic layers were combined, and evaporated. The residue was purified by flash chromatography (0 to 30% EtOAc/Hexane) to give 4-fluoro-2-methylene-2,3-dihydro-1H-inden-1-one (249b) (3.91 g, 72%). LC-MS tR=1.49 min in 3 min chromatography, MS (ESI) m/z 163 [M+H]+

Provenance & Evidence