IonPairEnantRadical : Transforming Enantioselective Radical Chemistry using Ion Pairing Catalysis

Radical reactions, in which electrons move singly rather than in pairs, have seen an immense pace of development in recent years. These exciting developments, many of which produce stereocentres, have served to highlight the ongoing challenge of rendering radical reactions enantioselective. Whilst many of the key enantiocontrol strategies from the two-electron world have been applied, these are ineffective in many situations and each strategy possesses specific limitations. We are broadly interested in an approach to catalysis that utilises attractive non-covalent interactions between catalyst and substrate to draw the two close and better exercise control. Particularly, ion-pairing is one of the most fundamental and powerful non-covalent interactions but is frequently underexplored by synthetic chemists as a controlling force, perhaps due to concerns regarding directionality and predictability. However, we believe that they present unique opportunities to exert selectivity control where conventional strategies fail. In this proposal we outline an ambitious program which will apply innovative and unexplored ion-pairing strategies to control enantioselectivity in a variety of important radical chemistries for which there are no or limited existing methods for imposing control. In catalytic cycles involving photoredox catalysis, whilst charge is usually appropriately indicated on intermediates, the associated counterion is rarely depicted or even attempted to be tracked in most reports. We believe that, far from being insignificant, counterions can play crucial roles in the control of enantioselectivity - in a catalytic cycle where there is little scope for leveraging existing modes of asymmetric catalysis, the counterion can provide the key. This proposal consists of four "challenge areas", as defined in the four Work Plans. These represent important and topical classes of radical transformations that have little or no precedent to be carried out asymmetrically using existing approaches. If the approaches outlined herein can be proven viable then there are numerous other reaction types to which they can be applied and we hope that this may open new horizons in the field.