The concept of Gallium-controlled double C-H functionalization of aliphatic CH₂-groups driven by Vinyl carbocations

The direct C-H activation of inert C(sp³)-H bonds in a hydrocarbon chain has been a very attractive target in organic synthesis for many decades. Among all the variety of processes, those driven by vinyl carbocations are quite scarce thus far, and it is hard to control for unstabilized vinyl cations. In this study, we designed a double C(sp³)-H functionalization of unactivated alkyl CH₂ groups to produce a totally substituted quaternary carbon stereocenter via insertion of vinyl carbocations. These processes represent complicated reaction cascades with high molecular complexity controlled by the cooperative action of Ga(III) salts & GaHal₄^- anions and allow one-step deep poly-functionalization of simple CH substrates to be performed. In practice, this concept was initially implemented with simple starting compounds such as alkyl acetylenes and activated cyclopropanes, alkenes, or cyclobutanes to construct norbornane, cyclopentatetralin, and other important skeletons.