Perchloric Acid → Ethyl 2-(4-bromo-2,5-dimethylthiophen-3-yl)-2-(tert-butoxy)acetate

HRID 591054Notes

Reaction equation

[Br:1][C:2]1[C:3]([CH:9]([OH:15])[C:10]([O:12][CH2:13][CH3:14])=[O:11])=[C:4]([CH3:8])[S:5][C:6]=1[CH3:7].Cl(O)(=O)(=O)=O.C(=O)(O)[O-].[Na+]>C(OC(=O)C)(C)(C)C>[Br:1][C:2]1[C:3]([CH:9]([O:15][C:3]([CH3:9])([CH3:4])[CH3:2])[C:10]([O:12][CH2:13][CH3:14])=[O:11])=[C:4]([CH3:8])[S:5][C:6]=1[CH3:7]

Participants

Conditions

Temperature: -5 °C

Procedure

To a suspension of ethyl 2-(4-bromo-2,5-dimethylthiophen-3-yl)-2-hydroxyacetate (28d) (830 mg, 2.83 mmol) in tert-butylacetate (29 mL) at −10° C. was added perchloric acid (1 mL). The mixture was stirred at −5° C. for 1 hour. The mixture was then basified with a saturated aqueous solution of sodium bicarbonate until pH 8. The aqueous layer was extracted with ethyl acetate. The organic layer was washed with brine, dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate 90/10) to afford the desired product (28e) as a colorless oil (870 g, 2.49 mmol, 88%).

Workup

extractionThe aqueous layer was extracted with ethyl acetate
washThe organic layer was washed with brine
dry with materialdried over sodium sulfate
filtrationfiltered
concentrationconcentrated under reduced pressure
customThe residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate 90/10)

Sources & evidence

ORD record: ord-b68248f8469a4b8291d1162b4010b481
Source dataset: uspto-grants-2016_01
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US09238026B2

Reaction notes

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