Cope Elimination
The Cope reaction or Cope elimination is an elimination reaction commonly used in organic chemistry. This transformation involves the stereoselective syn elimination of tertiary amine oxides. These substrates (amine oxides) are easily prepared by the oxidation of the tertiary amine with a peroxide. Common peroxides include hydrogen peroxide and peroxycarboxylic acids such as mCPBA.
General features:
1. One-pot reaction. Isolation of the tertiary amine oxide is not required. 2. The amine is mixed with the oxidizing agent and heated. 3. The reaction takes place at lower temperatures (100–150 ºC) than the Hofmann Elimination. 4. Clean reaction with few to none side reactions.
Cope Elimination
Reaction Mechanism
This transformation involves the stereoselective syn elimination of tertiary amine oxides. These amine oxide substrates are easily prepared by the oxidation of the tertiary amine with a peroxide. Common peroxides include hydrogen peroxide and peroxycarboxylic acids such as mCPBA.
Experimental Procedure
To a round bottom flask equipped with a magnetic stir bar was added the amine (0.32 mmol, 1.0 eq) and DCM (3.10 mL). The solution was cooled in a dry ice/acetone bath and stirred at this temperature for 10 minutes before the addition of mCPBA (1.0 eq) as a solution in DCM, which was added dropwise to keep the solution temperature consistent. Upon completion of addition, basic alumina, Al2O3, (0.66 g/mmol of substrate) was added to the solution and was stirred 20 seconds at this temperature before the solution quickly passed through a plug of basic alumina. Concentration and purification of the filtrate via silica gel flash column chromatography afforded the desired alkene.
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