Controlled interconversion of macrocyclic atropisomers via defined intermediates.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39095340.
- Also identified by DOI 10.1038/s41467-024-50739-6 and PMC identifier 11297318.
- Licence recorded as CC BY-NC-ND.
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Abstract
Macrocyclic conformations play a crucial role in regulating their properties. Our understanding of the determinants to control macrocyclic conformation interconversion is still in its infancy. Here we present a macrocycle, octamethyl cyclo[4](1,3-(4,6)-dimethylbenzene)[4]((4,6-benzene)(1,3-dicarboxylate) (OC-4), that can exist at 298 K as two stable atropisomers with C<sub>2v</sub> and C<sub>4v</sub> symmetry denoted as C<sub>2v</sub>-OC-4 and C<sub>4v</sub>-OC-4, respectively. Heating induces the efficient stepwise conversion of C<sub>2v</sub>- to C<sub>4v</sub>-OC-4 via a C<sub>s</sub>-symmetric intermediate (C<sub>s</sub>-OC-4). It differs from the typical transition state-mediated processes of simple C-C single bond rotations. Hydrolysis and further esterification with a countercation dependence promote the generation of C<sub>2v</sub>- and C<sub>s</sub>-OC-4 from C<sub>4v</sub>-OC-4. In contrast to C<sub>2v</sub>-OC-4, C<sub>4v</sub>-OC-4 can bind linear guests to form pseudo-rotaxans, or bind C<sub>60</sub> or C<sub>70</sub> efficiently. The present study highlights the differences in recognition behavior that can result from conformational interconversion, as well as providing insights into the basic parameters that govern coupled molecular rotations.