The ability of π-π interactions to stabilize a complementary transition state can provide a significant reaction barrier lowering for the stereoinversion of polyaromatic hydrocarbons (PAHs). In this context, the class of cyclophanes is especially interesting as catalyst as it can provide suitable binding pockets to surround guest molecules and offers both binding strength and selectivity by shape complementarity. Due to their large π-surfaces, which afford high binding affinities for PAHs, we considered our recently introduced perylene bisimide (PBI) based cyclophane hosts as particularly promising candidates for the catalysis of stereoinversions. In this context, we designed the first example of an inherently chiral PBI cyclophane host, which shows a very high binding affinity for the complexation of [4]- and [5]-helicene. For [5]-helicene the template-catalyzed deracemization into an enantioenriched mixture was demonstrated with an enantiomeric excess (<i>ee</i>) of 66%. Further elaboration of these cyclophanes and kinetic experiments as well as theoretical calculations are ongoing that will help to understand the origin of the accelerated stereoinversion for different substrates within PBI-based cyclophane cavities.

Catalysis of enantiomerization within a perylene bisimide cyclophane template

ACS Spring 2022

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