Tetra‐tert‐butyltetraphosphacubane: The First Thermal Cyclooligomerization of a Phosphaalkyne

A previously unknown reaction of phosphaalkynes, the thermal cyclotetramerization of 1, leads in one step to the title compound 2 (65 h at 130°C in a glass pressure tube, neat). Compound 2 is pale yellow and air stable. The NMR signals of the cage atoms are unusual: δ(13C)= −29.07, δ(31P)= + 257.4.