While bicyclo[1.1.1]pentanes (BCPs) and bicyclo[3.1.1]heptanes (BCHeps) serve as established 3D bioisosteres for para- and meta-substituted benzenes, accessible via ring-opening of their corresponding propellanes, the integration of heteroatoms into these propellane scaffolds has remained elusive. Herein, the authors report the practical synthesis of 3-oxa/aza[3.1.1]propellanes, two heteroatom-containing analogues of propellane, from 1,5-diiodo-3-hetero-BCHeps.