title: Bis-tert-Alcohol-Functionalized Crown-6-Calix[4]arene: An Organic Promoter for Nucleophilic Fluorination.
abstract: A bis-tert-alcohol-functionalized crown-6-calix[4]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-calix[4]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.
authors.affiliation: Department of Chemistry, Inha University, 100 Inha-ro, Nam-gu, Incheon, 402-751, Korea), Fax: (+82) 32-867-5604.
authors.forename: Vinod H
authors.initials: VH
authors.lastname: Jadhav
authors.affiliation: Department of Chemistry, Inha University, 100 Inha-ro, Nam-gu, Incheon, 402-751, Korea), Fax: (+82) 32-867-5604.
authors.forename: Wonsil
authors.initials: W
authors.lastname: Choi
authors.affiliation: Department of Applied Chemistry, Kyung Hee University, Gyeonggi, 446-701, Korea.
authors.forename: Sung-Sik
authors.initials: SS
authors.lastname: Lee
authors.affiliation: Department of Applied Chemistry, Kyung Hee University, Gyeonggi, 446-701, Korea. sylee@khu.ac.kr.
authors.forename: Sungyul
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Inha University, 100 Inha-ro, Nam-gu, Incheon, 402-751, Korea), Fax: (+82) 32-867-5604. kimdw@inha.ac.kr.
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Kim
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D047250:Calixarenes / Q000737:chemistry*; D002412:Cations / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D054879:Halogenation; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D006860:Hydrogen Bonding; D008670:Metals / Q000737:chemistry; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000438:Alcohols; D002412:Cations; D043844:Crown Ethers; D006845:Hydrocarbons, Fluorinated; D008670:Metals; D010710:Phosphates; D013438:Sulfhydryl Compounds; D047250:Calixarenes; C012980:fluorophosphate; D000431:Ethanol; D005459:Fluorides
keywords: alkali metals; calixarenes; fluorination; phase-transfer catalysis; promoters