Bismuth Radical Catalysis: Thermally Induced Intramolecular C(sp)-C(sp) Cyclization of Unactivated Alkyl Iodides and Alkynes.

Bismuth radical chemistry has attracted increased interest in recent years. Here, we report a series of bismuth-manganese complexes that catalyze the intramolecular redox-neutral coupling of alkyl iodides and alkynes under purely thermal conditions. Computational studies support the design of catalyst candidates, aiming to achieve low Bi-Mn bond homolytic dissociation energies. The radical nature of the cyclization reaction was supported by EPR spectroscopic spin trap experiments. This underexplored mode of thermally induced radical reactivity was applied to construct a variety of cyclic vinyl iodide compounds, including drug derivatives.