Memory of chirality in reactions involving monoradicals

Abstract

The effects of memory of chirality (MoC) in reactions involving monoradical species are reviewed here. Reactions involving a nonracemic chiral starting material bearing a single stereogenic element such as a chiral center or chiral axis directly involved in the new bond formation are discussed. These reactions lead to a nonracemic product via an intermediate susceptible to rapid racemization. Memory of chirality has been observed in cyclic radicals, aryl, ester/amide substituted acyclic radicals, and benzylic radicals at temperatures up to 130 °C.

Keywords:

• Free radicals
• asymmetric synthesis
• conformation
• chirality
• atropisomers
• racemization
• stereochemistry

Acknowledgements

The Swiss National Science Foundation (Project 200020_152782), the State Secretariat for Education, Research and Innovation (SBFI Nr. C14.0096) and the Agence National de La Recherche (Project ANR Blanc 13 BS07-0010-01 “UZFul-Chem”) are gratefully acknowledged for financial support. The COST Action CM1201 has generously supported a short-term scientific mission of Christian Simon Gloor.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Notes

1 Single diastereomers may also show memory of chirality if only one chiral element is involved in a diastereospecific new bond formation via an intermediate susceptible to epimerize via a change of conformation (see Scheme 2 for such an example).