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1,3-Alternate calix[4]arenes, selectively functionalized by amino groups.
Crenguta Danila1, Michael Bolte, Volker Böhmer
1Fachbereich Chemie und Pharmazie, Abteilung Lehramt Chemie, Johannes Gutenberg-Universitat, Duesbergweg 10-14, D-55099, Mainz, Germany.
Organic & Biomolecular Chemistry
|December 17, 2004
Summary
This study details methods for synthesizing amino-functionalized calix[4]arenes in a fixed 1,3-alternate conformation. These versatile molecules enable selective functionalization on both rims for advanced chemical assemblies.
Area of Science:
- Supramolecular Chemistry
- Organic Synthesis
- Macrocyclic Chemistry
Background:
- Calix[4]arenes are versatile macrocyclic hosts with conformational flexibility.
- Selective functionalization of calix[4]arenes is crucial for creating complex molecular architectures.
- Achieving fixed conformations, like the 1,3-alternate, is key for predictable molecular design.
Purpose of the Study:
- To develop general strategies for synthesizing 1,3-alternate calix[4]arene derivatives with selective amino group placement.
- To demonstrate the utility of these amino-functionalized calix[4]arenes as building blocks for further chemical modifications.
- To enable selective functionalization of both the narrow and wide rims of the calix[4]arene scaffold.
Main Methods:
- O-alkylation of calix[4]arenes with omega-bromophthalimides or omega-bromonitriles to introduce precursors for amino groups on the narrow rim.
- Ipso-nitration of tert-butylcalix[4]arene derivatives followed by reduction to introduce amino groups on the wide rim.
- Selective protection strategies (e.g., Boc anhydride) and sequential functionalization to differentiate between molecular rims.
- Structural characterization using 1H NMR spectroscopy and single-crystal X-ray diffraction.
Main Results:
- Successful synthesis of calix[4]arenes fixed in the 1,3-alternate conformation, selectively substituted with amino groups on either the narrow or wide rim.
- Demonstration of selective functionalization on both rims, allowing for distinct chemical modifications (e.g., amide, urea, imide formation).
- Preparation of precursors for octaamines in the 1,3-alternate conformation with selectively activatable amino functions.
- Structural confirmation of synthesized compounds, distinguishing them from other conformational isomers.
Conclusions:
- Established robust synthetic routes for regioselectively amino-functionalized 1,3-alternate calix[4]arenes.
- These derivatives serve as versatile platforms for constructing complex molecules and supramolecular assemblies.
- The developed methodologies allow for precise control over functionalization, paving the way for chiral derivatives and advanced materials.