Mechanistic Insights into the Methylation and Formylation of Amines with CO₂: Exploring Diverse CO₂ Activation Models

The urgent need to address global warming and resource depletion has spurred research into sustainable methods for the utilization of CO₂ as a C1 source. However, the challenge remains in developing metal-free, cost-effective, and environmentally friendly approaches for CO₂ conversion. Here, we investigate the mechanisms of CO₂ activation in the methylation and formylation of amines using both theoretical and experimental approaches. Our study reveals that the methylation process is complex, with the "double H model" proving most effective, while the formylation reaction is more straightforward, favoring the "single H model." Control experiments confirmed these distinct activation models by monitoring the HCOOH formation. We further evaluated key influencing factors, including Hirshfeld charge and nucleophilicity. Based on our findings, we successfully designed new reactions, demonstrating the practical applications of these mechanisms. This research provides valuable insights into CO₂ conversion strategies, advancing the field of sustainable chemistry.