Stereoselective Palladium-Catalyzed 1,3-Arylboration of Unconjugated Dienes for Expedient Synthesis of 1,3-Disubstituted Cyclohexanes

As significant pharmacophores, 1,3-disubstituted cyclohexanes are widespread in natural products and synthetic bioactive molecules. In this work, we describe a palladium-catalyzed arylboration of 1,4-cyclohexadienes, which allows expeditious access to an array of functionalized 1,3-disubstituted cyclohexanes from the readily available starting materials. Palladium catalysis enables the arylboration to proceed in a reversed regioselectivity compared with earlier nickel catalysis. The most striking feature of this protocol lies in the 1,3-regioselectivity and exclusive cis-diastereoselectivity. Intriguingly, the success of this three-component reaction does not rely on the application of dative ligands but a cheap ammonium chloride salt instead. The synthetic utility of this method is highlighted by a series of downstream stereospecific transformations and a drug molecule synthesis.