Ever since the first isolation,[1] stable carbenes have gained tremendous importance as ancillary ligands for catalytically active transition-metal complexes and as organocatalysts in their own right.[2] To increase the structural range, our group has recently reported the prototype of a new class of singlet carbene ligands.[3] Specifically, deprotonation of the alkenyl phosphonium salt 3a with potassium hexa- ...
