Since its first synthesis in 1959 , bicyclo[1.1.0]butane (BCB) has captured the imagination of chemists due to its innate strain energy and relative ease of assembly and handling . The highly diverse reactivity of BCB-containing compounds, facilitated by the release of strain upon breaking the bridging C1-C3 bond, has allowed such structures to become valuable building blocks for the generation of sp -rich carbocycles and heterocycles . Perhaps the most prominent reactivity mode that has been utilised in this context is the addition of nucleophiles and nucleophilic radicals to the bridgehead of electron-deficient BCB compounds (Fig. ). In recent years, alternative strategies have also emerged, such as electrophilic addition , reduction or Lewis acid activation of adjacent carbonyl fragments to trigger ring- opening, pyridine-boryl radical transfer and photochemical excitation of the strained bridging bond to access the corresponding diradical . Employing these strategies has led to the development of many unique transformations and, as a consequence, BCB-containing compounds have become cemented as valuable tools in areas such as bioconjugation and in the assembly of challenging arene isosteres .