Divergent Synthesis of Möbius and Hückel N‐Heterocycloarenes From a Common Macrocyclic Backbone

Abstract

ABSTRACT We report the divergent synthesis of a Möbius N‐heterocycloarene ( 1 ) and a Hückel N‐heterocycloarene ( 2 ) from a common macrocyclic precursor. The topology is governed by the annulation reaction: the Scholl reaction yields the Möbius topology, while InCl 3 ‐mediated alkyne annulation gives the Hückel topology. In acyclic models, both reactions favor C4/C5 over C2/C7 bond formation, but this regioselectivity reverses in the constrained macrocycle. The Scholl reaction forms three bonds at C2, one at C7, and two at C5—one inducing the 180° twist for the Möbius topology and the other accompanied by a skeletal rearrangement, whereas alkyne annulation exclusively forms C2/C7 bonds to afford the Hückel topology. Crystal structure analysis and computational studies show uneven contortion in 1 and localized aromatic ring currents in both 1 and 2 . Compound 2 adopts a saddle‐shaped geometry with high conformational flexibility and binds tetrafluoroborate via C–H···F hydrogen bonds in solution.