Diethyl Oxalate → (3,4,5-Tribromothiophen-2-yl)-oxo-acetic acid ethyl ester

HRID 1166211

Reaction equation

[Br:1][C:2]1[S:6][C:5](Br)=[C:4]([Br:8])[C:3]=1[Br:9].C([Li])CCC.[C:15](OCC)(=[O:21])[C:16]([O:18][CH2:19][CH3:20])=[O:17]>>[CH2:19]([O:18][C:16](=[O:17])[C:15]([C:5]1[S:6][C:2]([Br:1])=[C:3]([Br:9])[C:4]=1[Br:8])=[O:21])[CH3:20]

Participants

Reactant 3

HCID 7268Diethyl Oxalate

HCID 77565Tetrabromothiophene

HCID 178418339Butyllithium

Product 1

HCID 69968494(3,4,5-Tribromothiophen-2-yl)-oxo-acetic acid ethyl esterYield 71.3%

Conditions

Temperature: -18 °C

Procedure

To tetrabromothiophene (2.0 g, 5.0 mmol) in an oven dried 50 mL flask, evacuated and flushed with nitrogen, was added anhydrous diethyl ether (12 ml). The resulting solution was cooled to −18° C., then n-butyllithium (1.6 M in hexane) (3.1 ml, 5.0 mmol ) was added dropwise via a syringe. After stirring for 10 min at −18° C., diethyl oxalate (0.75 ml, 5.5 mmol) was added dropwise. Stirring was continued for 30 min, then the reaction mixture was quenched with 1N HCl. The organic layer was separated, dried over Na2SO4 and concentrated under vacuum. Purification was performed by column chromatography using hexane/ethyl acetate (20:1) to yield (3,4,5-tribromothiophen-2-yl)-oxo-acetic acid ethyl ester as a yellow solid (1.5 g, 71%). MS (M+H)+: 422.55; 1H NMR (300 MHz, CDCl3) δ4.45 (2H, q, J=7.1 Hz), 1.44 (3H, t, J=7.1 Hz). 13C NMR (75 MHz, CDCl3) δ173.89, 161.64, 133.35, 124.81, 123.05, 122.54, 63.75, 14.11.

Workup

customevacuated
customflushed with nitrogen
additionwas added anhydrous diethyl ether (12 ml)
stirringStirring
waitwas continued for 30 min
customthe reaction mixture was quenched with 1N HCl
customThe organic layer was separated
dry with materialdried over Na2SO4
concentrationconcentrated under vacuum
customPurification

Sources & evidence

ORD record: ord-885df1cb6ab84dbcbca378dcb9067489
Source dataset: uspto-grants-2003_09
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06613786B2

Linked notes

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