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]

HRID 594882Notes

Reaction equation

[CH2:1]([Li])CCC.[Br:6][C:7]1[CH:8]=[C:9]2[C:16](=[CH:17][CH:18]=1)[O:15][C:14]([CH3:20])([CH3:19])[C:11]1([CH2:13][CH2:12]1)[C:10]2=O>[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.O1CCCC1>[Br:6][C:7]1[CH:8]=[C:9]2[C:16](=[CH:17][CH:18]=1)[O:15][C:14]([CH3:20])([CH3:19])[C:11]1([CH2:13][CH2:12]1)[C:10]2=[CH2:1]

Participants

Conditions

Temperature: 0 °C

Procedure

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).

Workup

temperaturecooling
stirringThe mixture was stirred for 1 hour at 0° C
customThe reaction was quenched
additionby adding water
extractionextracted with ethyl acetate
washThe organic layer was washed with brine
dry with materialdried over anhydrous magnesium sulfate
concentrationconcentrated in vacuo
customThe residue was purified by silicagel column chromatography (hexane/ethyl acetate=20:1-10:1)

Sources & evidence

ORD record: ord-75deb37f810742f692be770eb1477749
Source dataset: uspto-grants-2016_01
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US09242973B2

Reaction notes

Loading…