Keck Radical Allylation

First reported separately by Masanori Kosugi and Jean Grignon in 1973, the coupling of an alkyl halide with allyltributyltin under radical conditions to insert an allyl group was employed in the total synthesis of perhydrohistrionicotoxin by Gary Keck and colleagues. After he had determined the scope of this reaction, it became known as the Keck radical allylation. Azobisisobutyronitrile (AIBN) was found to be the most efficient catalyst in initiating the process, and the reaction was found to be general for primary, secondary, and tertiary alkyl bromides. The reaction is highly chemoselective, tolerates a wide range of functional groups, and is tolerant of steric hindrance.

This reaction has been utilized successfully in a number of total synthesis campaigns, including that of the Stemona alkaloid (-)-tuberostemonine (by Peter Wipf), and the anti-cancer alkaloid manzamine A (by David J. Hart).