In recent years, bicyclo[1.1.0]butanes (BCBs) have garnered significant attention as versatile building blocks in organic synthesis. The high ring-strain resulting from their inter-bridgehead C1-C3 bond has proven instrumental in various transformations. More interestingly, the insertion of one-, two-, or three-carbon atoms to this strained bond via formal [n+2] cycloaddition reaction emerged as a powerful approach to access substituted bicyclo[1.1.1]pentanes (BCPs), bicyclo[2.1.1]hexanes (BCHs), and bicyclo[3.1.1]heptanes (BCHeps). While numerous elegant transformations have been reported for the synthesis of such bicyclo[n. 1.1]alkanes, the methods for accessing related heterobicyclo[n. 1.1]alkanes remain under-explored. Analogous to carbon atom insertions, the strategic development of efficient methods for the highly selective insertion of different heteroatomic units into BCBs could be an ideal approach to access diverse heterobicyclo[n.1.1]alkanes (Fig. ). However, mitigating the undesired pathways associated with the reaction of heteroatomic precursors with BCBs such as nucleophilic ring-opening and isomerization reaction could pose considerable challenges along this direction. Recently, our group and Leitch group reported the insertion of two-heteroatomic units of benzoylformates, aldehydes, and imines to BCBs yielding 2-oxa and 2-azabicyclo[2.1.1]hexanes, respectively. However, methodologies for the insertion of one-or three-heteroatomic units into BCBsleading to sought-after heterobicyclo[1.1.1]pentanes and heterobicyclo[3.1.1]heptanes -remain evidently unexplored. (3'). Although seemingly straightforward, this endeavor involves a number of challenges: 1) ensuring the stability of the expected products 3 or 3' under photocatalytic conditions; 2) addressing the regioselectivity of amidyl radical addition across BCBs; 3) suppressing the isomerization of BCBs to cyclobutenes I, and circumventing the aziridination of cyclobutenes, which could result in fused azabicyclopentanes III; and 4) addressing the addition of benzoyl nitrenes or amidyl radicals to BCBs followed by facile deprotonation, leading to undesired non-cyclized product II. By overcoming these challenges, herein, we report the highly regio-and chemoselective insertion of amidyl radicals to BCBs, providing access to novel 2-oxa-4-azabicyclo[3.1.1]hept-3-enes. These newly synthesized heterobicyclic motifs are structurally rigid and exhibit well-defined exit vectors which are important molecular properties in medicinal chemistry. Moreover, the rich downstream chemistry offered by these compounds further underscores their synthetic utility in accessing structurally complex molecules.