Separation of the Enantiomers of 2,2′‐Dihydroxy‐1, 1′‐binaphthyl and 10,10′‐Dihydroxy‐9,9′‐biphenanthryl by Complexation with N ‐Alkylcinchonidinium Halides

The separation of racemates of C 2 ‐symmetric biaryldiols , important starting materials for numerous ligands in asymmetric synthesis, can be achieved by using commercially available cinchonidinium halides 1 , X = Cl, Br. In the first separation step inclusion complexes are formed from 1 and the diol; the alkyl substituent at the bridgehead N atom is decisive for the complexation behavior.