Visible light-mediated Alder-ene reaction of bicyclobutanes with cyclohexynes to access skipped dienes and skeletal remodeling to tetralines

Abstract

The strain-release driven reactions of bicyclo[1.1.0]butanes (BCBs) offer a powerful synthetic strategy for the construction of complex carbocyclic frameworks. Herein, we report the direct engagement of BCBs with transient cyclohexynes through a visible light-mediated dual-strain release manifold. By utilizing a photochemical peroxide precursor, this catalyst-free protocol bypasses the deleterious byproducts and super-stoichiometric fluoride sources typically required for cyclohexyne generation. This methodology allows the streamlined synthesis of skipped dienes bearing an all-carbon quaternary centre that are otherwise difficult to access via traditional means. The versatility of this reaction is underscored by its excellent functional group tolerance, scalability, and successfully extended to benzynes under mild and ambient conditions. Furthermore, the synthetic utility is demonstrated through the late-stage diversification of bioactive molecules and a synergistic S8/DMSO-mediated skeletal remodeling of skipped dienes to functionalized tetralines. A visible-light-mediated Alder-ene reaction between cyclohexynes and bicyclobutanes is presented, bypassing harsh conditions to couple two highly strained systems. This strategy provides efficient access to C(sp3)-rich skipped dienes and skeletally remodeled tetralins.