Lewis Acid-Catalyzed Formal [2π+2σ] Cycloaddition of Bicyclobutanes with Quinoxalin-2(1H)-ones: Access to Quinoxaline-Fused Aza-Bicyclo[2.1.1]hexanes

)-ones, facilitated by Lewis acid catalysis, is presented. This reaction is carried out under mild conditions and exhibits a broad substrate scope and excellent functional group tolerance.