Chapter 14. Unusual Aspects of Asymmetric Induction and Amplification Observed in the Soai Reaction

Abstract

Asymmetric autocatalysis, that is, the Soai reaction, has an enormous power to amplify the chiral effects of catalysts or ligands. Although they can control the enantioselectivity in asymmetric reactions, their sense of enantioselectivity might be changed by the influence of other factors, such as achiral/chiral additives and reaction temperature. Asymmetric autocatalysis with amplification of enantiomeric excess (ee) can sensitively detect and enhance such factors as seemingly unusual chiral effects to give highly enantioenriched (S)- or (R)-5-pyrimidyl alkanols, even though the influence is slight. Moreover, while examining the asymmetric autocatalysis of bis(pyrimidyl alkanols) with conformationally flexible long alkyl spacers, rapid enhancement of ee was observed with a remarkable decrease of the fraction of meso-compounds in the reaction products. Thus, ultra-remote intramolecular 1,39-asymmetric induction, based on the principle of the direct orientation of catalytic and reactive moieties, is discussed in this chapter.