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Hydrogenation with Diimide

Reduction of Alkenes with Diimide: Experimental Procedure

The reduction is carried out at room temperature. Since diimide is an unstable compound, it has to be generated in situ for the reaction. Several methods are available for the generation of diimide.

Examples for the generation of diimide:

  • oxidation of hydrazine with hydrogen peroxide
  • oxidation of hydrazine with oxygen and Cu(II)
  • fragmentation of azodicarboxylic acid

Reaction of the generated diimide with alkenes is immediate and produces the desired product.

Azodicarboxamide is a good starting material for the most convenient in situ generation of diimide.

Fig.1
Fig.2

Preparation of potassium azodicarboxylate:

To a stirred aqueous solution of 40% potassium hydoxide is added at 0°C 5,0 g of azodicarboxamide within 2 h. Stirring is continued for an additional 60 min at 0°C. The yellow precipitate is filtered and washed with ice-cold methanol to yield after drying in high vacuum 7,3 g (87 %) of potassium azodicarboxylate as a fine, crystalline powder .

Reduction:

To a solution of 2,0 mmol alkene and 480 mg (2,5 mmol ) of potassium azodicarboxylate in 50 mL of methanol a solution of 0,7 mL (12 mmol ) of glacial acetic acid dissolved in 5 mL of methanol is slowly added dropwise at room temperature. The reaction mixture is stirred for several hours and subsequently worked up.

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