Reaction #1121794

Reaction equation

1-(4-bromo-pyridin-2-yl)-4,4-dimethoxy-butan-1-one

1-(4-Bromo-pyridin-2-yl)-4,4-dimethoxy-butan-1-one

trifluoroacetic acid

→

4-(4-bromo-pyridin-2-yl)-4-oxo-butyraldehyde

4-(4-Bromo-pyridin-2-yl)-4-oxo-butyraldehyde

Solvents

CH2Cl2

Conditions

Workup

1. 1
   ConcentrationThe reaction is concentrated
2. 2
   workup.DISSOLUTIONthe residue dissolved in ethyl acetate (150 mL)
3. 3
   Washwashed with water 3 times
4. 4
   Dryingdried over Na2SO4
5. 5
   Otherthe solvent evaporated
6. 6
   OtherThe residue is purified by flash column chromatography (30% EtOAc in hexanes)

Procedure

To a solution of 1-(4-bromo-pyridin-2-yl)-4,4-dimethoxy-butan-1-one (2) (crude from Step 2, 11 g, 38.2 mmol) in 100 of CH2Cl2 at room temperature is added trifluoroacetic acid (10.9 g, 95.4 mmol) and the reaction mixture is stirred overnight. The reaction is concentrated, the residue dissolved in ethyl acetate (150 mL) and washed with water 3 times. The organic layers are combined, dried over Na2SO4 and the solvent evaporated. The residue is purified by flash column chromatography (30% EtOAc in hexanes) to give 4-(4-bromo-pyridin-2-yl)-4-oxo-butyraldehyde (3) as an yellow oil. (4.16 g, 45%): MS ES+244.04.

Source