Radical-Polar Crossover Catalysis with a d0 Metal Enabled by a Redox-Active Ligand

Radical-polar crossover mechanisms are invoked in numerous late transition metal and photocatalyzed reactions. To the best of our knowledge, reductive radical-polar crossover mechanisms are not invoked for group 3 early transition metals due to their propensity to exist in high oxidation states. Through use of a redox-active (tris)amido ligand we have accessed this mechanism for use with early transition metals. This mechanism is showcased through enabling product formation for a wide variety of elimination products from alpha-halo substituted benzylic bromides. The mechanism of this new type of reactivity with Sc is explored, and Hammett analysis reveals an anionic intermediate. The wide functional group tolerance of this reaction is also demonstrated.