The introduction of heteroatoms into bicyclo[n.1.1]alkane frameworks confers further desirable benefits on physicochemical properties compared to their carbocyclic parents, particularly in the case of BCHeps where the larger ring size in the saturated 3-carbon bridge reduces hydrophilicity 4 ; in addition, these heterocyclic bicyclo[n. 1.1]alkanes also have the potential to act as bioisosteres for heteroarenes such as pyridines. For example, approaches to 3-azacyclic analogues (3-aza-BCHeps) have been reported (Fig. ) through the stepwise insertion of heteroatom-containing three-atom motifs such as azomethine ylids 16 , isocyanides , and vinyl azides into the inter-bridgehead bond of bicyclo[1.1.0]butanes (BCBs). While successfully generating the 3-aza-BCHep scaffold, these methods suffer from limitations in the diversity of functionalities that can be introduced at the aza-BCHep bridgehead positions due to synthetic restrictions in BCB stability and activation mechanism necessitating an electron-withdrawing group, as well as installing specific substituents on their threeatom bridges. An alternative, scalable strategy described by Mykhailiuk and co-workers employs the reduction of a nitrile-functionalised spirocyclic cyclobutane-oxetane to trigger aza-BCHep formation , which invariably positions a hydroxymethyl group at one of the bridgehead carbons atoms; benefits to metabolic stability, solubility and lipophilicity were noted compared to analogous pyridines. Despite other scaffolds such as 2-aza-18,20 , 2-oxa-21 and 2-thia-BCHeps 22 , as well as bisheterocyclic analogues being accessible (albeit also with limitations in substituent scope), other attractive motifs, such as 3-oxa-and 3-thia-BCHeps, remain unexplored.