One‐Pot Multimolecular Macrocyclization for the Expedient Synthesis of Macrocyclic Aromatic Pentamers by a Chain Growth Mechanism |
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Authors: | Bo Qin Sheng Shen Chang Sun Dr Zhiyun Du Prof?Dr Kun Zhang Dr Huaqiang Zeng |
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Institution: | 1. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543 (Singapore), Fax: (+65) 6779‐1691;2. Faculty of Chemical Engineering and Light Industry, Guang Dong University of Technology, Guang Dong, 510006 (China) |
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Abstract: | POCl3‐mediated one‐pot macrocyclization allows the highly selective formation of five‐residue macrocycles that are rigidified by internally placed intramolecular hydrogen bonds. Mechanistic investigation by using tailored competition experiments and kinetic simulation provides a comprehensive model, supporting a chain‐growth mechanism underlying the one‐pot formation of aromatic pentamers, whereby the successive addition of a bifunctional monomer unit onto either another monomer or the growing oligomeric backbone is faster than other types of bimolecular condensations involving oligomers longer than monomers. DFT calculations at the B3LYP/6‐31G* level reveal the five‐residue pentamer to be the most stable with respect to alternative four‐, six‐, and seven‐residue macrocycles. These novel mechanistic insights may become useful in analyzing other macrocyclization, oligomerization, and ploymerization reactions. |
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Keywords: | foldamers hydrogen bonds macrocycles macrocyclization mechanism supramolecular chemistry |
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