Manganese(I)‐Catalyzed Enantioselective C(sp²)−C(sp³) Bond‐Forming for the Synthesis of Skipped Dienes with Synergistic Aminocatalysis

Mn(I)‐catalyzed enantioselective C−C bond‐forming reactions represent a great challenge in homogeneous catalysis primarily due to a limited understanding of its mechanistic principles. Herein, we have developed an interesting catalytic strategy that leverages a synergistic combination of a dimeric manganese(I) catalyst and a chiral aminocatalyst to address this issue. A range of conjugated dienals and trienals can exclusively proceed 1,4‐hydroalkenylation by using readily available aromatic and aliphatic alkenyl boronic acids as coupling partners, producing a rich library of skipped diene aldehydes in synthetically useful yields and high levels of enantioselectivities. Notably, downstream transformations of these products can not only afford a concise approach to construct enantioenriched skipped trienes but also realize enantioselective total synthesis of analogues to (−)‐Blepharocalyxin D in four steps. DFT calculations suggest the 1,4‐hydroalkenylation is kinetically more favorable than 1,6‐hydroalkenylation.