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Wolff Rearrangement

March 4, 2013

Wolff Rearrangement is a organic rearrangement reaction in which α-diazoketones are decomposed thermally or photochemically undergoes rearrangement to form ketenes. This reaction is named after a German chemist Ludwig Wolff in 1912. Normally these ketenes cannot be isolated because it is more reactive and tend to form diketenes.

Wolff rearrangements that are conducted in the presence of nucleophiles generate derivatives of carboxylic acids, and in the presence of unsaturated compounds can undergo [2+2] cycloadditions. Wolff Rearrangement in the presence of nucleophiles results in a one-carbon homologation of carboxylic acids.

For example, consider the following reaction

Wolff Rearrangement

Mechanism of the reaction

  • The carboxylic acid reacts with thionyl chloride to form carbonyl chloride.
  • The diazo carbanion attacks the carbonyl carbon to form azo intermediate.
  • Carbene is generated by the removal of nitrogen.
  • When carbene reacts with water ketene is generated.
  • Ketene on further hydrolysis generates the product.

Wolff Rearrangement mechanism

Examples

Predict the products for the following reaction

Wolff Rearrangement mechanism

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