Examples of Regioselective Anion Recognition among a Family of Two‑, Three‑, and Four-“Armed” Bis‑, Tris‑, and Tetrakis(thioureido) [n]Polynorbornane hosts

A family of conformationally preorganized, [n]polynorbornane-based anion hosts 1a,b–6a,b have been synthesized. The series includes receptors with 4, 8, and 12 H-bond donors. Using 1H NMR titration techniques, evaluation of the new hosts against a series of alkyl and aryl dicarboxylates as well as a range of phosphoanionic species has revealed that the tris(thioureido) hosts (in particular 3a) are capable of regioselectively binding dicarboxylates and pyrophosphate (H2PPi2–).