Biaryls, most notably 1,1′-binaphthalene derivatives (eg 1[1]and 2[2]), occupy a prominent position among C 2 -symmetric chiral auxiliaries and ligands for asymmetric synthesis.[3]By contrast, spiranes, another class of molecules with axial chirality,[4]have received relatively little attention from the point of view of ligand design. In fact, only derivatives of cis,cis-spiro[4,4]nonane-1,6- diol 3 appear to have been employed in asymmetric synthesis.[5]Crown ethers ...
