title: Oligoethylene glycols as highly efficient mutifunctional promoters for nucleophilic-substitution reactions.
abstract: Herein, we report the promising use of n-oligoethylene glycols (oligoEGs) as mutifunctional promoters for nucleophilic-substitution reactions employing alkali metal salts. Among the various oligoEGs tested, pentaethylene glycol (pentaEG) had the most efficient catalytic activity. In particular, when compared with other nucleophiles examined, a fluorine nucleophile generated from CsF was significantly activated by the pentaEG promoter. We also performed various facile nucleophilic-displacement reactions, such as the halogenation, acetoxylation, thioacetoxylation, nitrilation, and azidation of various substrates with potassium halides, acetate, thioacetate, cyanide, and sodium azide, respectively, in the presence of the pentaEG promoter. All of these reactions provided their desired products in excellent yields. Furthermore, the combination of pentaEG and a tert-alcohol medium showed tremendous efficiency in the nucleophilic-displacement reactions (fluorination and methoxylation) of base-sensitive substrates with basic nucleophiles (cesium fluoride and potassium methoxide, respectively). The catalytic role of oligoEGs was examined by quantum-chemical methods. The oxygen atoms in oligoEGs were found to act as Lewis bases on the metal cations to produce the "flexible" nucleophile, whereas the two terminal hydroxy (OH) groups acted as "anchors" to orientate the nucleophile and the substrate into an ideal configuration for the reaction.
authors.affiliation: Department of Nuclear Medicine, Cyclotron Research Center, Research Institute of Clinical Medicine, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-712, Korea.
authors.forename: Vinod H
authors.initials: VH
authors.lastname: Jadhav
authors.forename: Seung Ho
authors.initials: SH
authors.lastname: Jang
authors.forename: Hwan-Jeong
authors.initials: HJ
authors.lastname: Jeong
authors.forename: Seok Tae
authors.initials: ST
authors.lastname: Lim
authors.forename: Myung-Hee
authors.initials: MH
authors.lastname: Sohn
authors.forename: Ju-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Sungyul
authors.initials: S
authors.lastname: Lee
authors.forename: Ji Woong
authors.initials: JW
authors.lastname: Lee
authors.forename: Choong Eui
authors.initials: CE
authors.lastname: Song
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Kim
mesh_terms: D000438:Alcohols / Q000737:chemistry; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D005030:Ethylenes / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry*; D006018:Glycols / Q000737:chemistry*; D008672:Metals, Alkali / Q000737:chemistry; D008968:Molecular Conformation; D015394:Molecular Structure
chemical_list: D000438:Alcohols; D005030:Ethylenes; D006018:Glycols; D008672:Metals, Alkali; D005461:Fluorine