Discovery and organocatalytic enantioselective construction of axially chiral cyclohexadienylidene skeletons

Studies of axial chirality have advanced to become an integral part of modern chemistry research, especially in asymmetric catalysis. Most investigations have revolved around catalytic enantioselective construction of the privileged axially chiral scaffolds, whereas the discovery of alternative scaffolds lags far behind. Described here is the exploitation of axially chiral molecules that are derived by substituting one C=C double bond of allenes with a cyclohexadienyl moiety. Structurally diverse analogs could be accessed in high efficiency with excellent stereocontrol through two facile and direct synthetic strategies, namely CPA-catalyzed asymmetric dearomatization strategy and enantioselective condensation strategy. Notably, the sterically bulky CPA catalyst plays a central role in the extraordinary levels of chemo-, site-, and enantioselectivities of the dearomatization strategy. These findings not only expand the current library of axially chiral compounds but also offer additional insights to explore other axially chiral scaffolds with different skeletal frameworks.