Visible Light‐Induced Synthesis of Fluorenes from α‐Biaryldiazoacetates

Carbenes are pivotal reactive intermediates for accessing a wide range of complex molecules, which are frequently used in chemical synthesis and medicinal advancement. We have developed a convenient approach to fluorenes from α ‐biaryldiazoacetates via low‐energy blue light‐induced photochemical generation of a carbene intermediate, where the reaction took place at room temperature without any catalysts, bases, or oxidants in acetonitrile. The present catalyst‐free and operationally simple approach enables highly efficient annulation of α ‐biaryldiazoacetates under mild reaction conditions.