Electronic Effects of Substituents on the Stability of N-Heterocyclic Carbene-Carbodiimide Adducts
N-heterocyclic carbenes (NHCs) are powerful and versatile organocatalysts which have shown success with reactions such as lactide polymerization. However, free NHCs are unstable in air. To make NHCs easier to handle outside an airfree environment, several “masks,” such as CO2, have been tested. Upon application of heat, the mask reversibly releases the NHC, triggering catalysis. We aim to use carbodiimides (CDIs) as a more tunable replacement for CO2 so the release of the catalyst can be varied independently of its activity. My project investigates how the stability of the NHC-CDI adduct depends on the electron-donating/electron-withdrawing character of the substituents on the CDI. We have demonstrated that more electron-donating substituents promote the release of the NHC at lower temperatures. Current trends and future directions will be discussed.