Iridium-Catalyzed Enantioselective Allylation of Alkynylboronates to Access Chiral 1,4-Dienes

Skipped dienes, particularly 1,4-dienes, play significant roles in pharmaceuticals and organic synthesis as they serve as key intermediates for the construction of complex structures and also bioactive molecules. However, the catalytic assembly of this motif with high stereoselectivity from readily available starting materials remains a substantial synthetic challenge. Herein, we reported a direct iridium-catalyzed enantioselective allylation reaction with allylic electrophiles and alkynyl boronates, resulting in various 1,4-dienes with excellent Z/E ratios and enantioselectivity. The reaction proceeds through a concerted mechanism that involves an allylation-induced 1,2-migration of the alkynyl boronate, followed by a syn-addition of the migrating group and Ir(π-allyl) complex across the alkynyl fragment to selectively deliver the more challenging Z-alkenes. DFT calculations clarify the origins of the observed high chemo- and stereoselectivity. Furthermore, this method demonstrates a broad substrate scope, and the resulting enantiomerically enriched 1,4-diene products can be readily derivatized.