With an understanding of the accessibility and physical properties of BCB radical cations, a reactivity regime that cannot be achieved using previously known strategies was pursued. Specifically, we targeted [2π+2σ] cycloaddition reactions to access bicyclo[2.1.1]hexane (BCH) compounds, highly valuable isosteres of orthoand meta-substituted benzene that are sp 3 -rich with well-defined substituent exit vectors . Although [2π+2σ] cycloaddition reactions that harness the strained bond of BCB have been reported by our own research group , as well as those of Brown 21 , Procter , Leitch and others , in all cases, alkenes that can be employed require either a radical stabilising group, electron-withdrawing group or heteroatom directly appended to the double bond, depending on the respective mechanism (Fig. ). Conversely, it is known that styrene-type radical cations , intermediates that display remarkably similar levels of charge and spin delocalisation to 1a •+ (see Supplementary Information for details), have the ability to participate in [2π+2π] cycloaddition reactions with olefins that are not stabilised by an adjacent π-system or carbonyl unit . Therefore, we believed that harnessing BCB radical cations could provide a general method for [2π+2σ] cycloaddition reactions, allowing the transformation to occur with multiple distinct classes of olefins, including simple feedstock alkenes that have so far been elusive.