ChemInform Abstract: High Symmetry Chiral Auxiliaries Containing Heteroatoms

Based on l,l'-binaphthalene-2,2'-diol 1. that is considered the prototype of the class of "man-made" chiral auxiliaries possessing C2 symmetry, a variety of other chiral molecules containing the binaphthyl or biphenyl skeleton has been developed. Among them, 1 ,l'-binaphthalene- 2,2'-dithiol 2 is the one that has experienced the largest assortment of applications. "Man made" chiral auxiliaries are becoming increasingly popular over the classic auxiliaries directly derived from the natural chiral pool. Especially popular are those based on the binaphthyl skeleton (1) not only because of the high degree of optical induction that they provide, but also because these molecules incorporate a number of features that "natural" chiral auxiliaries rarely possess. For example, the high-symmetry chirality (C2-symmetry), the direct attachment of the functional groups to an aromatic system, the high crystallinity, the simple spectra, the possibility to access both enantiomers and the versatility to attach almost any functional group make them suitable for any occasion. Well known representative examples of this class of molecules are l.l'-binaphthalene-2,2'- diol 1 (2) and the dithiol2 (3).