Organic compounds containing three-dimensional saturated polycyclic units with quaternary carbon centres hold significant value and application potential in fields such as medicine, biology, chemical engineering, materials science, asymmetric organic synthesis and agriculture. In recent years, the successful application in clinical trials of innovative drug molecules and bioactive molecules designed and developed using the ‘escape from flatland' concept in medicinal chemistry, as well as analogues of bioisosteric scaffolds containing aromatic rings synthesised using bioisosterism, has brought these molecules to the forefront of attention in numerous fields of research. However, the limited availability of direct natural sources and inefficient and time-consuming traditional synthetic strategies have consistently hindered the research and practical application of such compounds. Although two-dimensional (hetero)aromatics—which are diverse, widely sourced, and largely inexpensive and readily available—serve as potential reaction precursors for these compounds, their inherent reactivity inertness makes it an extremely challenging task to study their direct ‘dimensional upgrade' transformation to in situ construct Csp3-rich three-dimensional organic scaffolds. In interdisciplinary research across fields such as green organic synthesis, catalysis, pharmaceuticals and biology since the beginning of the 21st century, bicyclo[1.1.0]butane derivatives (BCBs)—with their unique structures—have emerged as highly potential, multifunctional molecular building blocks. Their efficacy in efficiently transforming (hetero)aromatic compounds into three-dimensional polycyclic complex molecules of greater practical value has been progressively demonstrated, leading to the development of a series of novel synthetic strategies. Herein, we systematically summarize and overview progress made over the past years in the utilization of bicyclo[1.1.0]butane derivatives for (hetero)aromatics dearomatisation and construction of 3D cyclic polycyclic molecules via cycloaddition reaction under Lewis acid catalysis, visible-light-driven organic catalysis (including energy-transfer catalysis and single electron transfer catalysis) and other hybrid catalytic systems, covering more than twenty cases, and also provide an outlook on promising future research and developments in this field facilitating a wider application of three-dimensional polycyclic molecules and emergence of novel design ideas.

Key words: bicyclo[1.1.0]butanes, [σ+π] cycloaddition, Lewis acid catalysis, organic photocatalysis, (hetero)aromatic dearomatisation, 3D polycyclic molecule