ABSTRACT
The point-to-helical chirality transfer utilizing a traceless chiral auxiliary features a remarkable independence from the diverse structural perturbations allowing for the preparation of both parent and functionalized fully aromatic helicenes in enantiomer ratios of >99:<1. Although there is still a way to go in order to develop a practical and general asymmetric synthesis of enantiopure helicenes, the recent achievements indicate that a solution to this problem present since the birth of helicene chemistry in 1956 is possible. Importantly, various synthetic methodologies were published to transform nonracemic biaryl precursors into nonracemic helicenes, thus demonstrating an excellent relay of stereochemical information when transforming axial chirality into helicity. The first promising attempts at this were already reported, and therefore, there are prospects to develop a general, practical and short catalytic asymmetric synthesis of enantiopure helicenes. Derivatives of nonracemic helicenes were found to respond reversibly to external stimuli constituting thus intriguing chiroptical switches.
