Recent Advances in the Cascade Cyclization of Alkyne Units for the Construction of Benzofluorenes

Benzofluorenes are an important class of polycyclic aromatic hydrocarbons (PAHs), which are widely used in materials science for light-sensitive electronic components. In addition, the benzofluorene skeleton also serves as a key structural unit in various natural products. Therefore, the development of synthetic strategies for the construction of benzofluorenes has been a prominent research topic in synthetic chemistry. Over the past few decades, numerous efforts have been made for the construction of benzofluorenes via cascade cyclization of alkyne units. This review aims to summarize recent advances in the cascade cyclization of alkyne units for the construction of Based on the different reaction mechanisms underlying these transformations, this review can be divided into four categories: (1) thermal-induced cascade cyclization of alkyne units for the construction of benzofluorenes, (2) metal-catalyzed cascade cyclization of alkyne units for the construction of benzofluorenes, (3) acid-promoted/catalyzed cyclization of alkyne units for the construction of benzofluorenes, and (4) base-promoted cascade cyclization of alkyne units for the construction of benzofluorenes.