Barton Decarboxylation

The radical decarboxylation of a Barton ester proceeds to the corresponding alkane after treatment with tributyltin hydride or t-butylmercaptan:

An alternative possibility is the introduction of a substituent by reaction with a suitable radical trapping agent:

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Mechanism of the Barton Decarboxylation

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-Sn 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:

The Barton Decarboxylation offers several options for the introduction of substituents - some examples are shown below:

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Recent Literature

Synthesis of 6-functionalized tricyclodecadienones using Barton's radical decarboxylation reaction. Generation of tricyclo[5.2.1.0^2,6]decatrienone, a norbornene annulated cyclopentadienone

Synthesis of (-)-Ilimaquinone via a Radical Decarboxylation and Quinone Addition Reaction