Strain-release transformations of bicyclo[1.1.0]butanes and [1.1.1]propellanes

Bicyclo[1.1.0]butanes (BCBs) and [1.1.1]propellanes (tricyclo[1.1.1.01,3]pentanes, TCPs) are structurally unique compounds with different chemical properties. Strain-release driven reactions have emerged as an atom- and step-economic strategy for the organic synthesis. Using this strategy, a variety of functional ring molecules have been efficiently synthesized, including various cyclobutane molecules, bicyclo[2.1.1]hexanes, bicyclo[1.1.1]pentanes, and others. More specifically, these strain release-driven reactions include aspects of nucleophilic addition, radical addition, electrophilic or transition metal catalysis. This review will discuss the recent developments in the strain-release transformations of bicyclo[1.1.0]butanes and [1.1.1]propellanes.