Electron Upconversion Enables CP and CS 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.