Cycloelimination of Imidazolidin-2-ylidene N-Heterocyclic Carbenes: Mechanism and Insights into the Synthesis of Stable NHC-CDI Amidinates

We report the discovery that 1,3-bis(aryl) imidazolidin-2-ylidenes, one of the most widely studied classes of N-heterocyclic carbenes (NHCs), undergo quantitative conversion to zwitterionic NHC-CDI amidinates upon heating to approximate to 100 degrees C in solution. The mechanism of this novel NHC decomposition process is studied in detail. These studies enabled the rational synthesis of a new class of bench stable amidinates from a panel of NHCs and carbodiimides. We expect these constructs to find utility in a variety of applications.