Cu-catalyzed enantioselective synthesis of axially chiral diaryl ethers by ring-opening of cyclic iodonium salts

The efficient construction of axially chiral diaryl ethers (ACDEs) is an important, emerging but challenging task in organic synthesis. Existing success based on desymmetrization was limited to acyclic substrates and mono-modification of only one of the four substituents with low modularity. Here we developed the first enantioselective approach that allows concomitant modification of two substituents across both aryl rings, thus permitting flexible diversification of such ACDE structures. A mild copper-catalyzed approach based on ring-opening of cyclic diaryl iodonium salts was achieved, leading to excellent efficiency and enantioselectivity as well as good regioselectivity under mild conditions. Mechanistic studies revealed that ring-opening by the copper catalyst is rate-determining and enantio-determining. The highly enantioenriched ACDE products can serve as effective chiral catalysts for asymmetric synthesis.