Intramolecular hydrogen bonding and anion binding of N-benzamido-N'-benzoylthioureas.

N-(p-Dimethylamino)benzoyl-N'-phenylthiourea as an N-acylthiourea is known to be unable to bind anions due to a strong intramolecular hydrogen bond (IHB). We show here that by inserting an amido group in the N'-phenyl side the newly designed N-benzamido-N'-benzoylthioureas, despite this IHB too, bind strongly to anions with binding constants on the order of 10(6)-10(7) mol(-1) L. Results suggest that potential anion receptors or organocatalysts could be developed on the basis of this framework with a wide structural diversity.