Iptycenes are three-dimensional blade-shaped molecules, which have been used extensively in supramolecular chemistry, crystal engineering, and functional π-conjugated macromolecules. We recently reported the chemistry of "triazoliptycene", in which 1,2,3-triazole has formally replaced one of the three phenyl rings of the iconic triptycene molecule. A last-stage regioselective C-N cross-coupling of triazoliptycene allowed for facile access to a library of fluorescent N-aryl triazole derivatives displaying unique photophysical properties. Key to the success of this chemistry is a strong bias toward the 2H- rather than the 1H-tautomer of the triazoliptycene, which we ascribed to the electronically-driven thermodynamic bias to diminish the C-C double bond character of the iptycene-fused triazole fragment. The invention (not discovery) of the parent triptycene molecule by Bartlett in the 1940's was prompted by genuine curiosity into the exceptional properties of bridgehead C–X bonds and bond dissociation mechanisms. In this presentation, we will discuss a combined experimental-theoretical study to better understand yet another "iptycenyl effect" from the perspectives of cross-coupling reactions and mechanisms.

Iptycenyl effect: Primary vs. secondary stereoelectronic bias of bridged bicyclic molecular skeleton

2019 Spring National Meeting

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