Indoles are the basis of many compounds of biological interest, including the plant hormone Auxin and tryptamine alkaloids such as serotonin and melatonin.  The ability to radiohalogenate indoles in a way that is compatible with a variety of functional groups would enable the study of these and other biological systems by PET and SPECT.  Due to the higher specific activities obtained with nucleophilic radiohalogenation as compared with electrophilic conditions, we used halodemetallations to introduce radioactive halogens onto the indole scaffold.  While the C2 and C3 positions of the indole have been the typical sites for metallation reactions, palladium-catalyzed transmetallations at the C5 and C6 positions of the scaffold have been less thoroughly explored.  We will discuss the challenges we have encountered in the synthesis of these metallated indole derivatives, and the parameters that played a role in the successful metallation and subsequent radiohalogenations of these compounds.

Preparation of C5 and C6-metallated indole derivatives as precursors for radiohalogenation

243rd National Meeting (2012)

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