Divergent Synthesis of Chelating Aziridines and Cyclic(Alkyl)(Amino)Carbenes (CAACs) from Pyridyl-Tethered Robust Azomethine Ylides.

Azomethine ylides are typically in situ generated synthons for making N-heterocycles through cycloaddition reactions. But an offbeat aspect about them is the isomeric nature of aldiminium-based azomethine ylides and (alkyl/aryl)(amino)carbenes, interconvertible by a formal 1,3-H transfer. Herein, two thermally robust azomethine ylides with a N-appended picolyl sidearm are isolated, which cyclize to aziridines at 80 °C but unprecedentedly result CAAC-CuCl (CAAC=cyclic(alkyl)(amino)carbene) complexes when heated with CuCl at merely 60 °C. The pendant N , as revealed by computational analysis, plays a crucial role in this unusual 1,3-H shift using a deprotonation-protonation sequence, as well as in placing the CuCl at the carbenic site in tandem. The softer nature of Cu is also critical. Chelating CAACs are rare and one with a N-tethered additional donor is priorly unknown. Both CAAC and aziridine are bidentate chelators giving highly active cationic Rh catalysts for hydrosilylating unactivated olefins by Et SiH. Notably, the aziridine-Rh is superior than the CAAC-Rh catalyst.