Following bromination of the residual alcohol (17, 92%), reaction with MeLi gave 3-N-Ts-[3.1.1]propellane 5 as a solution in THF. Remarkably, diffusion of an ether/pentane mixture into this solution afforded crystals of 5, which unlike carbocyclic propellanes did not undergo spontaneous polymerisation to a BCHep-staffane. Instead, this solid proved suitable for single crystal X-ray diffraction, enabling the acquisition of the first crystal structure of a small-ring propellane (Fig. , see the Supplementary Information for details). It is possible that the unexpected stability of this propellane can be ascribed to the inductive electron-withdrawing effect of the sulfonamide nitrogen atom, which renders the inter-bridgehead bond less electron rich, reducing the usual destabilising Pauli repulsion with adjacent C-C bonds .