Question

Propose three different decarboxylation pathways

Answer 1

Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO₂). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain.

Decarboxylations are the bases of many named reactions. These include

• Barton decarboxylation- The Barton decarboxylation is a radical reaction in which a carboxylic acid is converted to a thiohydroxamate ester (commonly referred to as a Barton ester). The product is then heated in the presence of a radical initiator and a suitable hydrogen donor to afford the decarboxylated product. This is an example of a reductive decarboxylation. Using this reaction it is possible to remove carboxylic acid moieties from alkyl groups and replace them with other functional groups.
• Kolbe electrolysis- The Kolbe electrolysis or Kolbe reaction is an organic reaction named after Hermann Kolbe.The Kolbe reaction is formally a decarboxylative dimerisation of two carboxylic acids (or carboxylate ions).
• Kochi reaction- The Kochi reaction is an organic reaction for the decarboxylation of carboxylic acids to alkyl halides with lead(IV) acetate and a lithium halide.
• Hunsdiecker reaction- The Hunsdiecker reaction (also called the Borodin reaction or the Hunsdiecker–Borodin reaction) is a name reaction in organic chemistry whereby silver salts of carboxylic acids react with a halogen to produce an organic halide.^[1] It is an example of both a decarboxylation and a halogenation reaction as the product has one fewer carbon atoms than the starting material (lost as carbon dioxide) and a halogen atom is introduced its place.

All are radical reactions.

The Krapcho decarboxylation is a related decarboxylation of an ester.

The Tsuji–Trost reaction involves the intermediacy of an allyl complex.

In ketonic decarboxylation a carboxylic acid is converted to a ketone.