Theory and Defination :
Barton Decarboxylation is the organic reaction in which the conversion of a carboxylic acid to a thiohydroxamate ester followed by heating the product in the presence of a suitable hydrogen donor such as tri-n-butylin hydride, produces a reductive decarboxylation. This sequence of reaction is called the reaction and may be used to remove a carboxylic acid and replace it with other functional groups.This reaction is named after a British chemist and Nobel Prize laureate Sir Derek Barton.
General Reaction :
An alternative possibility is the introduction of a substituent by reaction with a suitable radical trapping agent:
Mechanism :
The initiation of the Barton Decarboxylation ( Bu3Sn-H -> Bu3Sn. ) is effected with a radical initiator, and as with the Barton-McCombie Deoxygenation, the driving force for the reaction itself is the formation of the stable S-Bond.
In addition, Barton esters can also be cleaved photolytically or thermally:
If an excess of a suitable radical trapping agent is present in the reaction medium, substitution will occur; otherwise, radical recombination takes place to give the pyridyl sulfide:
Application and Example :
1) Preparation of Aldolsterone Acetate
2) Preparation of Perhydrohistrionicotoxin
