More recently, by taking advantage of the ready availability and inherent ring strain of BCBs, 6b,9 the exploration of new strategies to the cycloaddition between BCBs and alkenes in the generation of various BCHs has attracted intensive attentions. According to the reported reaction processes, most methods could be categorized into two modes: 1) radical pathway; and 2) two-electron pathway (Scheme 1b). By utilizing the photoinduced energy transfer course, Glorius 6a and Brown 6b groups respectively described elegant cycloaddition of BCBs and alkenes toward bicyclo[2.1.1]hexanes. The reaction was initiated by the excitation of either alkene or BCB to generate a diradical intermediate. Li 7a and Wang 7c groups developed a boryl-pyridine catalytic system to activate BCB as a cyclobutyl radical intermediate. Meanwhile, Procter group applied SmI2 as a single electron reductant to achieve the insertion of electrondeficient alkene into BCB (Scheme 1b-1). 7b Very recently, Zheng group described a Ti-catalyzed formal cycloaddition of BCB and 2-azadienes to synthesize aminobicyclo[2.1.1]hexanes. 7e Lately, Glorius accomplished the coupling of phenol and BCB by leveraging a photoredox process. 7d All the reactions above entailed the generation of radical species, which to some extent limited the substrate scope.