Heavy Atom Quantum Mechanical Tunneling in Total Synthesis.

Contributions from quantum mechanical tunneling to the rates of several radical coupling reactions between carbon sp 2 centers used as key steps in natural product total syntheses were computed using density functional theory. Contributions ranging from ∼15-52% from tunneling were predicted at room temperature, thereby indicating that tunneling plays an important role in the rates of these reactions and should perhaps be considered when designing complex synthetic schemes.