One-Pot Synthesis and AFM Imaging of a Triangular Aramide Macrocycle

Abstract

Macrocyclizations in exceptionally good yields were observed during the self-condensation of <i>N</i>-benzylated phenyl <i>p</i>-aminobenzoates in the presence of LiHMDS to yield three-membered cyclic aramides that adopt a triangular shape. An <i>ortho</i>-alkyloxy side chain on the <i>N</i>-benzyl protecting group is necessary for the macrocyclization to occur. Linear polymers are formed exclusively in the absence of this Li-chelating group. A model that explains the lack of formation of other cyclic congeners and the demand for an <i>N-</i>(<i>o</i>-alkoxybenzyl) protecting group is provided on the basis of DFT calculations. High-resolution AFM imaging of the prepared molecular triangles on a calcite(10.4) surface shows individual molecules arranged in groups of four due to strong surface templating effects and hydrogen bonding between the molecular triangles