o-Quinodimethane(o-QDM),a transient short-lived and highly reactive species,has attracted great curiosity from chemists over the past 40 years,both from theoretical and synthetic points of view.As cis-dienes,o-QDMs are much more reactive than the related “classical dienes”in Diels-Alder reactions(DA)with olefins.They were extensively used as versatile building-blocks to construct a variety of benzannulated system.However,the generation and trapping of the o-QDMs under mild conditions were still highly challenging due to its high reactivity.Although the photo-induced enolization of 2-alkylbenzaldehyde or pyrolysis of the benzo-cyclobutane under high temperature were reported in the literature,however,these conditions were highly limited because they are not applicable for irradiation-or heat-sensitive substrates.Recently,we developed a series of transition metal-catalyzed generation and trapping of the o-QDM to synthesis of different benzoannulated systems(Fig.1).