87823-45-8Relevant academic research and scientific papers
Studies of 9-fluorenyl carbocations. Intramolecular hydride migration in a substituted 9-fluorenyl carbocation
Mladenova,Chen,Rodriquez,Siu,Johnston,Hopkinson,Lee-Ruff
, p. 1109 - 1114 (2001)
The substituted fluorenyl cation, 9-(diphenylmethyl)fluoren-9-yl cation (4), is formed under stable ion conditions (low temperature/strong acid) from its corresponding alcohol 3. This ion is transformed to a substituted diphenyl methyl cation 8 at ambient temperature via an apparent 1,2-hydrogen shift. Irradiation of 9-(diphenylmethyl)fluoren-9-ol in methanol gives products derived from the corresponding cation along with radical-derived products from C-C and C-O homolysis processes. The laser flash photolysis of this alcohol gave a transient corresponding to cation 4. All of the photoproducts are derived from cation 4 or radical pathways. High level MO calculations point to a high barrier (23.8 kcal mol-1) for the 1,2-hydride shift. This barrier is the consequence of the minimum energy conformation of this fluorenyl cation which is less than ideal for the periplanar geometry necessary for this process.
Photochemical Pinacol Rearrangements of Unsymmetrical Diols
Mladenova, Gabriela,Singh, Gurmit,Acton, Austin,Chen, Lie,Rinco, Olga,Johnston, Linda J.,Lee-Ruff, Edward
, p. 2017 - 2023 (2007/10/03)
The photochemical pinacol reaction of a series of nonsymmetrical 9-fluorenyl-substituted vic-diols was investigated and compared with their acid-catalyzed thermal reaction. Unlike the thermal reaction, the radiation-induced processes involve only fluorenyl cations, as is reflected in differences of product distribution between the two reactions. From the product studies, substituent migratory aptitudes are reversed in the photochemical process, suggesting that kinetic control takes place under neutral conditions unlike the acid-catalyzed thermal reactions. The presence of fluorenyl cation intermediates and their lifetimes were established by laser flash spectroscopy studies.
Reaction of stannenes and phosphastannenes with aldehydes and ketones: New tin four-membered ring derivatives
Kandri Rodi,Anselme,Ranaivonjatovo,Escudié
, p. 965 - 972 (2007/10/03)
Stannene Tip2Sn=CR2 1 (Tip = 2,4,6-triisopropylphenyl, CR2 = fluorenylidene) enters a [2+2] cycloaddition reaction with benzophenone to afford the four-membered ring derivative 2. This stannaoxetane undergoes a [2+2] decom
Influence of Solvent and Cation on the Properties of Oxygen-containing Organic Anions. Part 4. Mechanism and Reactivity of Tetraaryloxirane Cleavage with Alkali Metals
Franco, M. Luisa T. M. B.,Herold, Bernardo J.,Maercker, Adalbert
, p. 119 - 129 (2007/10/02)
Six tetraaryloxiranes 1a-f (Scheme 4) were reduced (Schemes 1-3) with alkali metals (M = Li, Na, K, Cs) in eight polar aprotic solvents under an inert atmosphere.The organometallic solutions thus obtained were hydrolysed and the reaction products analysed.Similar experiments were carried out where the same solutions were quenched with D2O or MeI.In some cases the same solutions were studied by NMR and ESR spectroscopy before quenching.A stepwise reduction mechanism was established where the transfer of a first electron produces CO-bond scission in the oxirane ring, yielding a short-lived radical anion 4 or 5 (Scheme 1), i. e., a tetraalkyl-β-oxidoethyl radical.This intermediate can either eliminate oxygen as metal oxide (MO) to produce a tetraarylethylene 24 (Scheme 2) or be further reduced to a dianion 8 or 9 (Scheme 1).This anion yields, upon hydrolysis, low yields,if any, of the corresponding tetraphenylethanol 15 or 16 (Z = H).The larger proportion of the dianion, after the first protonation step, yielding anion 11 or 22, undergoes CC-bond scission which leads eventually to the corresponding ketone and diarylmethane 19 + 20 or 21 + 23 (Z = H) (Scheme 2).Other possible pathways were excluded through experiments where other possible intermediates were generated.These led to different end products.A triparametric linear correlation as a function of solvent parameters ETN and DN, as well as the cationic radius, was established for the influence of the nature of the solvent and counter-ion on the ratio between the rates of formation of products stemming from metal oxide (MO) elimination by the ring-opened radical anion 4 or 5 (Schemes 1 and 2) and rates of formation of products stemming from further reduction of the same radical anion to the dianion 8 or 9, thus confirming the mechanism established.
Substituent Effects on Electron Spin Distribution and Conformation of Radical Ions obtained from 9-Diphenylmethylenefluorenes
Franco, M. Luisa T. M. B.,Herold, Bernardo J.,Evans, Jeffrey C.,Rowlands, Christopher C.
, p. 443 - 450 (2007/10/02)
Nine new substituted 9-diphenylmethylenefluorenes were synthetized.The reductions of the unsubstituted hydrocarbon and eleven substituted derivatives were studied by cyclic voltammetry in dimethylformamide solution.E.s.r. and ENDOR spectra of the radical anions obtained by reduction with alkali metal in tetrahydrofuran were recorded.The electron spin distribution as obtained from experiment was compared with the results of Hueckel-McLachlan calculations.The conformations of the radical anions were determined from the spectra.The ratio of electron spin densities in the fluorene part of the alkene and in the diphenylmethylene group obeys a linear Hammett correlation.A similar study was performed for the radical cations of six of the twelve alkenes.
