Indol-2-ylidene (IdY): Ambiphilic N-heterocyclic Carbene Derived from Indole.

The synthesis of ambiphilic N-heterocyclic carbene ligand, indol-2-ylidene (IdY, A ), is described, as a series of indolenium precursors ( 2a - f ) were prepared on a gram scale in good yields. Trapping experiments with elemental selenium, [RhCl(cod)] 2 and CuCl provided the expected carbene adducts. Further computational and spectroscopic studies supported the ambiphilicity of IdY, which lies between Cyclic (alkyl)(amino)carbenes (CAAC-5) and cyclic (Amino)(aryl)carbene (CAArC). The copper complexes ( 6 ) show high percent buried volume (%V bur = 58.1) and allow for carboboration of terminal alkynes within 30 minutes in a demonstration of synthetic utility with good yields and high regioselectivity.