Doubly coarctate-stabilized carbenes: synthetic and computational studies.

Isoindazoles joined by an ethynyl linker to either a phenyltriazene or a phenyldiazene moiety were synthesized, and their subsequent reactivity was examined. Computations suggest that these molecules could rearrange at moderate temperatures via carbene intermediates that are doubly stabilized by coarctate conjugation. The experimental results corroborate the calculations, as the transient carbene can either be trapped with oxygen or undergo ring-opening to afford a rearranged product. Additional calculations illustrate some design principles that might lead to stable carbenes that are the global minimum on the coarctate hypersurface.