Helical-chiral small molecules in asymmetric catalysis

The design, synthesis and study of novel catalyst structures have had an enormous impact on asymmetric synthesis and continue to be a field of intense interest. Molecules with helical structures have fascinated chemists in the field for many years because such molecules are inherently chiral. A number of small molecules with such unique topology have been prepared in an optically active form and exploited as asymmetric catalysts. The story behind the development of these molecules is usually different in each case, in part due to differences in their synthetic accessibilities. This microreview provides some examples that illustrate the different ways in which such helical-chiral small molecules can be synthesized and used to catalyze reactions of interest, and highlights the beneficial effect of helical-chiral catalysts. Molecular frameworks characterized by a space curve exhibit helical chirality. In this microreview we discuss a variety of synthetic strategies used to construct helical-chiral small molecules and highlight their beneficial effects as asymmetric catalysts.