Boron trifluoride etherate → 4'-fluorospiro[cyclohexane-1,2'-indene]-1',4(3'H)-dione

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Reaction Conditions

Reaction Steps

To a solution of 4-fluoro-2-methylene-2,3-dihydro-1H-inden-1-one (249b) (3.71 g, 22.9 mmol) and (buta-1,3-dien-2-yloxy)trimethylsilane (5.2 mL, 29.8 mmol) in DCM (200 mL) at 0° C., there was added BF3.Et2O (0.5 mL dropwise. The resulting solution was stirred at 0° C. for another 30 min, quenched with MeOH (0.3 mL), warmed to room temperature, acidified with 2N HCl aqueous solution (15 mL) and extracted with DCM (10 mL×4). The combined organic layers were dried over Na2SO4, filtered and evaporated, and the residue was purified by flash chromatography (0 to 50% EtOAc/Hexane) to give 4′-fluorospiro[cyclohexane-1,2′-indene]-1′,4(3′H)-dione (249c) (2.77 g, 49%). LC-MS tR=1.41 min in 3 min chromatography, MS (ESI) m/z 233 [M+H]+.

Provenance & Evidence