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

Abstract

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.