Regioselective supramolecular catalysis. Exploiting multiple binding motifs in propanediurea molecular clips

Molecular clips derived from 2,4,6,8-tetraazabicyclo[3.3.1]nonane-3,7-dione promote increased regioselectivity in the SO2Cl2-mediated electrophilic aromatic chlorination of ortho-cresol leading to para/ortho ratios (Rp/o) <25; approximately six times larger than in the absence of the clip. Specific recognition events involving hydrogen-bond, π–π and dative covalent interactions are implicated.