Five- and six-membered N-H•••S hydrogen bonding in aromatic amides

The capacity of sulfur to form intramolecular five- or six-membered S center dot center dot center dot H-N hydrogen bonding in aromatic amides is assessed. The five-membered S center dot center dot center dot H-N hydrogen bonding is observed in crystal structures of five compounds, whereas the six-membered S center dot center dot center dot H-N hydrogen bonding is revealed in crystal structures of three compounds. The trityl group has been used to promote formation of the weak hydrogen bonding because it efficiently inhibits the competition of the intermolecular C=O center dot center dot center dot H-N hydrogen bonding. (2D) H-1 NMR experiments indicate that both patterns also exist in chloroform. (C) 2008 Elsevier Ltd. All rights reserved.