852534-09-9Relevant academic research and scientific papers
A versatile and conformationally adaptable fluorene-based receptor for efficient binding of silver cation
Rathore, Rajendra,Chebny, Vincent J.,Abdelwahed, Samen H.
, p. 8012 - 8013 (2005)
We have designed and synthesized a versatile fluorene-based receptor (1) in a one-pot reaction from readily available precursors, which adapts a deltaphane- or π-prismand-like conformer via a simple C-C bond rotation. Such a conformational adaptability of 1 allows it to bind a single silver cation with remarkable efficiency (K ～ 15000 M-1) as monitored by 1H NMR or UV-vis spectroscopy and further confirmed by competition experiments with tris[2.2.2]paracyclophane (or π-prismand 2) as well as a model compound 3 containing only one fluoranyl ring. Copyright
Hammett and Broensted-Type Relationships in Reactions of 9-Substituted Fluorenyl Anions with Benzyl Halides
Bordwell, Frederick G.,Hughes, David L.
, p. 3320 - 3325 (2007/10/02)
The rates of reaction of 9-substituted fluorenyl anions, 9-G-Fl- (G=CN, Ph, Me), with substituted benzyl chlorides (p-MeO, p-Me, m-Me, p-F, p-Cl, m-Cl, m-CF3, m-NO2) in Me2SO solution have been measured.A "U-shaped" Hammett plot was obtained for 9-CN-Fl- (ρmeta 1.3), but a "normal" Hammett plot was obtained with 9-Ph-Fl- (ρ = 1.8), which is 9.6 pK units more basic.Broensted-type plots of log k vs. pKa obtained for three 9-G-Fl- families (9-PhSO2, 9-PhS, and 9-Ph) reacting with m-CF3C6H4CH2Cl gave slopes (βNu) near 0.4.The βNu values for the 9-Ph-Fl- family reacting with ArCH2Cl were increased by the presence of electron accepting substituents, p-MeO (0.30), H (0.365), m-CF3 (0.45), m-NO2 (0.485).The small increases in Hammett ρ values and βNu values caused by electron-withdrawing substituents in ArCH2Cl are interpreted to mean that there is a small increase in the negative charge density in the benzylic carbon atom and/or chlorine atom in the transition state.Rates for the reaction of PhCH2Br with eight 9-G-Fl- anions were measured.For 9-CN-Fl- the kBr/kCl rate ratio was found to be 4 times larger in Me2SO than in EtOH.The reactivity-selectivity principle is discussed and the conclusion drawn that it should be abandoned.
