Electron Upconversion Enables CP and CS Bond Formation Under Mild Oxidative Conditions: A Theoretical Study

The formation of carbon–phosphorous (CP) and carbon–sulfur (CS) bonds is essential in organic synthesis, yet traditional methods frequently require strong oxidants that generate high‐energy carbocation intermediates and promote unwanted side reactions. In this work, we use density functional theory to examine an alternative mechanism that operates under basic conditions and involves three‐electron bond formation and concomitant electron upconversion. The radical‐anionic pathway involves an initial cyclization to form a 2‐center‐3‐electron bond, followed by oxidation of the upconverted radical‐anion by mild oxidants such as molecular oxygen. Our results show that this pathway is both thermodynamically and kinetically favored compared to conventional two‐electron routes when only mild oxidants are present, providing a more controlled and efficient strategy for CP and CS bond construction. These findings indicate that electron‐upconversion mechanisms can enable greener and more selective synthetic methods by reducing the dependence on strong oxidants and minimizing side reactions.