Enantioselective Synthesis of an Atropisomeric Diaryl Ether

Twisted ethers: Introduction of a bulky alkylsulfinyl substituent ortho to the C–O axis of a diaryl ether imposes a powerful conformational preference (see scheme). The preference persists upon oxidation of the sulfoxide to a sulfone, leading to dynamic thermodynamic resolution of the atropisomeric ether. This is the first enantioselective synthesis of an atropisomeric diaryl ether not forming part of a macrocyclic ring.