Bis‐tert‐Alcohol‐Functionalized Crown‐6‐Calix[4]arene: An Organic Promoter for Nucleophilic Fluorination |
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| Authors: | Dr Vinod H Jadhav Wonsil Choi Sung‐Sik Lee Prof?Dr Sungyul Lee Prof?Dr Dong Wook Kim |
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| Affiliation: | 1. Department of Chemistry, Inha University, Incheon, Korea), Fax: (+82)?32-867-5604;2. Department of Applied Chemistry, Kyung Hee University, Gyeonggi, Korea |
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| Abstract: | A bis‐tert‐alcohol‐functionalized crown‐6‐calix4]arene (BACCA) was designed and prepared as a multifunctional organic promoter for nucleophilic fluorinations with CsF. By formation of a CsF/BACCA complex, BACCA could release a significantly active and selective fluoride source for SN2 fluorination reactions. The origin of the promoting effects of BACCA was studied by quantum chemical methods. The role of BACCA was revealed to be separation of the metal fluoride to a large distance (>8 Å), thereby producing an essentially “free” F?. The synergistic actions of the crown‐6‐calix4]arene subunit (whose O atoms coordinate the counter‐cation Cs+) and the terminal tert‐alcohol OH groups (forming controlled hydrogen bonds with F?) of BACCA led to tremendous efficiency in SN2 fluorination of base‐sensitive substrates. |
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| Keywords: | alkali metals calixarenes fluorination phase-transfer catalysis promoters |
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