Installing tungsten Fischer carbene complexes into a calixarene framework

The synthesis of the first examples of calix[4]arene-based Fischer carbene complexes is reported here. Fischer carbene complex 2 is the key intermediate to reach uracil-like derivatives 3 and 4. X-ray and NMR studies revealed that the uracyl-like synthon gives rise to a supramolecular dimer. The organometallic calixarene complexes showed a promising cytotoxicity towards human tumor cell lines.