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An enaminone-directed benzannulation/macrocyclization approach to cyclophane ring systems.
F Christopher Pigge1, Fatemeh Ghasedi, Nigam P Rath
1Department of Chemistry and Biochemistry, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri 63121-4499, USA. piggec@jinx.umsl.edu
The Journal of Organic Chemistry
|June 22, 2002
Summary
Researchers developed a modular method to create functionalized cyclophane ring systems using a regioselective cross-benzannulation reaction. This approach allows for diverse cyclophane structures with varying tether compositions and ring sizes.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
Background:
- Cyclophanes are macrocyclic organic compounds with unique structural and electronic properties.
- Developing modular and efficient synthetic routes to functionalized cyclophanes is crucial for their application in various fields.
Purpose of the Study:
- To establish a straightforward and modular preparative approach for synthesizing 1,3,5-triaroylbenzene-based functionalized cyclophanes.
- To demonstrate the versatility of the method by creating cyclophanes with diverse bridging units.
Main Methods:
- A key macrocyclization step involving regioselective cross-benzannulation between bis(aryl ethynyl) ketone and enaminone reactants.
- Synthesis of macrocyclic products with ring sizes ranging from 18 to 22 members.
- Modification of the tether composition connecting aryl ethynyl ketone fragments.
Main Results:
- Successful construction of 18- to 22-membered cyclophane ring systems.
- Synthesis of cyclophanes with xylyl, alkyl, di(ethylene triamine), and di(ethylene oxy) bridging units.
- Isolated yields for the synthesized cyclophanes ranged from 11% to 46%.
Conclusions:
- The developed method provides a versatile and modular route to diverse functionalized cyclophanes.
- Structural characterization of three new cyclophanes (calixarene-like macrocycles 8 and 9, and crownophane 18) by X-ray diffractometry validates the synthetic approach.