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

Abstract

Macrocyclizations in exceptionally good yields were observed during the self-condensation of Nbenzylated phenyl p-aminobenzoates in the presence of LiHMDS to yield three-membered cyclic aramides that adopt a triangular shape. An ortho-alkyloxy side chain on the N-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 N-(o-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.

Synthesis and Structure of Optically Active Oligo(N‐substituted‐m‐benzamide)s Bearing a Bithiophene Chromophore on the Benzene Ring

“…Herein cis orientation for N ‐methyl amide in the starting conformation is substantially maintained during the energy minimization. Such a preference for cis isomer in N ‐alkyl amides is also theoretically demonstrated in other related compounds . Theoretical CD and absorption spectra of these conformers are shown in Figure .…”

“…However, the cis form is about 12 kJ mol −1 more stable than the trans , and the cis ‐to‐ trans transition is accompanied with a high barrier of ≈40 kJ·mol −1 . Thus the N ‐alkyl amide backbone should adopt a cis conformation predominantly, as also reported in other systems . Figure S19, Supporting Information, also shows the energy diagram for the reduced model in which all CO groups in rank 1 of 2‐mer were converted to CH 2 .…”

“…In 2‐mer, A1 and A2 angles (deg) were independently set to one of six values (45, 90, 135, 225, 270, and 315), while Am for the amide bond took 0 ( cis conformer): that is, 36 (6 × 6) conformations were built. In 3‐mer, four dihedral angles ( A1 , A2 , B1 , and B2 ) were independently changed with the above six values, whereas the two amide bonds were set to cis ( Am and Bm = 0): 1296 (36 × 36) were generated.…”

Advanced Developments in Cyclic Polymers: Synthesis, Applications, and Perspectives

“…After deprotection of N ‐( o ‐alkoxybenzyl) protecting groups, cyclic tri( p ‐benzamide) was obtained. The macro cycle exhibited a highly ordered two‐dimensional orientation on calcite surfaces …”

“…Intermolecular condensation of N-benzylated phenyl p-aminobenzoates in the presence of lithium bis(trimethylsilyl)amide (LiHMDS) could form at hree-membered triangular cyclic aramide ( Figure 3). [46] After deprotection of N-(o-alkoxybenzyl) protecting groups, cyclic tri(p-benzamide) was obtained. The macro cyclee xhibited ah ighly ordered two-dimensional orientation on calcite surfaces.…”