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 (H₂PPi^2–).