Using photoresponsive end-closing and end-opening reactions for the synthesis and disassembly of [2]rotaxanes: implications for dynamic covalent chemistry
| Autor: | Koichiro Akasaka, Suzuka Kakuchi, Youji Shimomura, Kenji Hisada, Yuji Tokunaga, Nobuharu Hashimoto, Shou Yamanaka |
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| Rok vydání: | 2009 |
| Předmět: |
Steric effects
Rotaxane Photoisomerization Rotaxanes Hydrogen bond Chemistry Organic Chemistry Dynamic covalent chemistry Hydrogen Bonding Photochemistry Photochemical Processes Chemical synthesis Combinatorial chemistry Organic Chemistry Phenomena Isomerism Stilbenes Solvents Self-assembly Isomerization |
| Zdroj: | The Journal of organic chemistry. 74(6) |
| ISSN: | 1520-6904 |
| Popis: | We have synthesized two [2]rotaxanes, each possessing a (Z)-alpha-methylstilbene unit as one of its stoppers, in good yield through the photoisomerization of terminal (E)-alpha-methylstilbene units of dialkylammonium salts in the presence of the crown ether dibenzo[24]crown-8 (DB24C8). The synthesis relies on the formation of pseudorotaxane intermediates through hydrogen bond-guided self-assembly and subsequent end-closing photoisomerization. An (E)-alpha-methylstilbene unit is not sufficiently bulky to prevent dissociation of the DB24C8 unit, whereas a (Z)-alpha-methylstilbene unit acts as a true stopper. We also synthesized these [2]rotaxanes from the (Z)-alpha-methylstilbene-terminated axle-like salts though thermodynamic covalent chemistry by taking advantage of the reversibility of the photoisomerization. To dissociate the components of the [2]rotaxanes, we performed the reverse end-opening process under UV irradiation (i.e., Z-to-E isomerization of the alpha-methylstilbene termini) in a polar solvent. These rotaxanes are stable at room temperature, but dissociate slowly to their two components at elevated temperatures. |
| Databáze: | OpenAIRE |
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