Nitrogen cation-pi interactions in asymmetric organocatalytic synthesis

Cation-pi interactions have been widely exploited and utilised in the structural biology arena, their fundamental importance in supramolecular chemistry and the pivotal role they play in host guest chemistry has rapidly expanded. In terms of organic synthesis pi-pi, CH-pi and cation-pi interactions are often invoked providing hypotheses for observed selectivities and reaction outcomes although fundamental studies of these interactions are less well reported, especially in the organic synthesis arena. This article considers cation-pi interactions in the field of asymmetric organocatalysis and provides a summary of cases where such interactions may play an important role. Importantly this article sets out to highlight where such interactions could be operating in order to highlight the potential wealth of investigations to be had in this area rather than categorically claiming such interactions are in operation. For asymmetric catalysis this is particularly important as the geometry of a transition state dictates the stereochemical outcome of the reaction, this article provides a perspective on such phenomena.