Barton's Protocol

Barton’s protocol allows for the addition of groups to the less substituted side of the carbon oxygen double bond. This is because the hydrazine can attack at this double bond then behave as a sort of leaving group in and SN2 type reaction once the iodine attacks. The formation of this structure is shown in the Barton paper:

This added iodine can then behave as a leaving group and allow the nucleophilic carbon-carbon double bond of molecule 17 to add to the molecule, thus creating molecule 18.



[Barton, D. H. R.; O’Brien, R. E.; Sternhell, S. J. Chem. Soc. 1962, 470-476.]