Copper-Catalyzed Asymmetric Alkynylation of <i>sp</i> ² Allenic C–H Bonds for the Synthesis of Skipped Diynes

Herein, we established a copper-catalyzed asymmetric alkynylation of the <i>sp</i>² C-H bond of silylallenes, which was presented as an efficient method for the synthesis of enantioenriched skipped diynes with excellent enantioselectivity. The reaction was initiated by hydrogen atom abstraction of <i>sp</i>² allenic C-H bonds, in which the resonance forms of allenic and propargylic radicals were chemo- and enantioselectively trapped by chiral alkynyl-Cu(II) species to deliver a variety of skipped diynes. The method features a broad substrate scope and robust functional group tolerance, accommodating both alkynyl silanes and boronic esters. Moreover, the resulting skipped diynes serve as versatile key synthons for incorporating enantiomerically enriched enynes, alkynes, alkanes, and their derivatives, which could be applied in the concise synthesis of several bioactive molecules.