6-bromo-2,2-dimethyl-4H-spiro[chromene-3,1'-cyclopropan]-4-one → 6-bromo-2,2-dimethyl-4-methylene-4H-spiro[chromene-3,1'-cyclopropane]

Participants

Reaction Conditions

Reaction Steps

To a suspension of methyl(triphenyl)phosphonium bromide (20.8 g, 58.2 mmol) in tetrahydrofuran (168 ml) was added n-butyllithium (2.69 M solution in hexane, 21.6 ml, 58.2 mmol) under dry ice-acetone bath cooling and argon atmosphere. The mixture was stirred for 1 hour at 0° C. To the mixture was added 6-bromo-2,2-dimethyl-4H-spiro[chromene-3,1′-cyclopropan]-4-one (8.18 g, 29 mmol). The mixture was stirred for 1 hour at 0° C. The reaction was quenched by adding water and extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous magnesium sulfate, and concentrated in vacuo. The residue was purified by silicagel column chromatography (hexane/ethyl acetate=20:1-10:1) to afford 6-bromo-2,2-dimethyl-4-methylene-4H-spiro[chromene-3,1′-cyclopropane] (7.69 g).

Provenance & Evidence